JavaScript Error in Chrome and Microsoft Edge when I click on tabs in Navbar

I got an error in JavaScript when I open my website in Chrome or MSEdge. Error is Uncaught TypeError: Cannot read properties of null (reading ‘toLowerCase’). When I open in Internet Explorer 11, it’s working perfectly. But in Chrome, when i click on tabs in Navbar, it got JS errors. May I know how can I fix that? I will insert both html and JavaScript.

    <?php
include("_include/checklogin.php"); 
include("_config.php");


echo "<html>";
echo "<head><title>" . $toolsname . "</title>";
echo "<link rel="stylesheet" type="text/css" href="web/jquery/css/custom-theme/jquery-ui-1.8.6.custom.css"/>";
echo "<script src="web/jquery/js/jquery-1.4.4.min.js" type="text/javascript"></script>";
echo "<script src="web/jquery/js/jquery-ui-1.8.6.custom.min.js" type="text/javascript"></script>";
echo "<script src="web/jquery/js/pointer_edge.js" type="text/javascript"></script>";
echo "<link rel="stylesheet" type="text/css" href="web/jquery/css/global.css">";

echo "<link rel="stylesheet" type="text/css" href="_local.css"/>";
echo "<script src="_tabadd.js" type="text/javascript"></script>";
echo "<script src="_tabedit.js" type="text/javascript"></script>";
echo "<script src="_tabhist.js" type="text/javascript"></script>";
echo "<script src="_tabProbSearch.js" type="text/javascript"></script>";
echo "<script src="probEquipProgram/_tabProbEquip.js" type="text/javascript"></script>";
echo "<script src="_common.js" type="text/javascript"></script>";
echo "</head>";
echo "<body>";

//include ($_SERVER['DOCUMENT_ROOT'] . "librarycommonapewsheader.php");
include("//sgewsnant21.amk.st.com/ewsweb/wwwroot/library/common7/apewsheader.php");

echo "<form name="equipment" method="post" target="_self">";
    echo "<div class="divprojname">" . $toolsname . "</div>";
    //<p align=center style="margin-top: -20px;"><font color=red size=3px><b>**Please Add New Equipment to ePCR**</b></font></p>
    echo "<div class="divcontainer">";
        echo "<div id=tabs style="width=100%;">";
            echo "<ul>";
                echo "<li><a href="#tabs-1">Edit Equipment</a></li>";
                echo "<li><a href="#tabs-2">Add Equipment</a></li>";
                echo "<li><a href="#tabs-3">Queue for Approval</a></li>";
                echo "<li><a href="#tabs-4">History</a></li>";
                echo "<li><a href="#tabs-5">Equip Config</a></li>";
                echo "<li><a href="#tabs-6">Prober Search Tool</a></li>";         
                echo "<li><a href="#tabs-7">Prober Equipment Program</a></li>";    
            echo "</ul>";
            echo "<div id=tabs-1>"; include("tabedit_filter.php"); echo "</div>";
            echo "<div id=tabs-2>"; include("tabadd_form.php"); echo "</div>";
            echo "<div id=tabs-3>"; include("tabque.php"); echo "</div>";
            echo "<div id=tabs-4>"; include("tabhist_filter.php"); echo "</div>";
            echo "<div id=tabs-5>";
                echo "<table cellpadding=2 cellspacing=2 align=center width=500px>";
                    echo "<tr>";
                        echo "<td>";
                            echo "<table cellpadding=0 cellspacing=0 width=100% style="border: 1px solid navy;">";
                                echo "<tr>";
                                    echo "<td nowrap valign=middle width=100% style="border-bottom: 1px solid" bgcolor=#6699CC>";
                                        echo "<table border=0 cellpadding=2 cellspacing=2>";
                                            echo "<tr><td><font class=ft10 color=navy><b>Tester and Prober Configuration</b></font></td></tr>";
                                        echo "</table>";
                                    echo "</td>";
                                echo "</tr>";
                                echo "<tr>";
                                    echo "<td nowrap valign=middle width=100%>";
                                        echo "<table border=0 cellpadding=2 cellspacing=2 width=90%>";
                                            echo "<tr>";
                                                // echo "<td align=left width="10%">&nbsp;   <a href="javascript:void();" onclick="javascript:FileDownload('http://sgewsweb.amk.st.com/webdata/tpmc/report/equip/APEWS_Testers_Config.xls');"><img border="0" src="".$grpnicon."xls.gif"></a></td>";
                                                echo "<td align=left width="10%">&nbsp;   <a href="javascript:void();" onclick="window.open('http://sgewsweb.amk.st.com/webdata/tpmc/report/equip/APEWS_Testers_Config.xlsx','_blank');"><img border="0" src="".$grpnicon."xls.gif"></a></td>";
                                                echo "<td align=left width="90%"><font class=ft10 color=#000000>APEWS Tester Configuration</font></td>";
                                            echo "</tr>";
                                            echo "<tr>";
                                                echo "<td align=left width="10%"><a href="javascript:void();" onclick="window.open('http://sgewsweb.amk.st.com/webdata/tpmc/report/equip/TEL - Configurations.pdf', '_blank')"><img border="0" src="".$grpnicon."pdf.gif"></a></td>";
                                                echo "<td align=left width="90%"><font class=ft10 color=#000000>TEL Configuration</font></td>";
                                            echo "</tr>";
                                            echo "<tr>";
                                                echo "<td align=left width="10%"><a href="javascript:void();" onclick="window.open('http://sgewsweb.amk.st.com/webdata/tpmc/report/equip/ACCRETECH - Configurations.pdf', '_blank')"><img border="0" src="".$grpnicon."pdf.gif"></a></td>";
                                                echo "<td align=left width="90%"><font class=ft10 color=#000000>ACCRETECH Configuration</font></td>";
                                            echo "</tr>";
                                            echo "<tr>";
                                                echo "<td align=left width="10%"><a href="javascript:void();" onclick="window.open('http://sgewsweb.amk.st.com/webdata/tpmc/report/equip/SEMICS - Configurations.pdf', '_blank')"><img border="0" src="".$grpnicon."pdf.gif"></a></td>";
                                                echo "<td align=left width="90%"><font class=ft10 color=#000000>SEMICS Configuration</font></td>";
                                            echo "</tr>";
                                            echo "<tr>";
                                                echo "<td align=left width="10%"><a href="javascript:void();" onclick="window.open('http://sgewsweb.amk.st.com/webdata/tpmc/report/equip/EG - Configurations.pdf', '_blank')"><img border="0" src="".$grpnicon."pdf.gif"></a></td>";
                                                echo "<td align=left width="90%"><font class=ft10 color=#000000>EG - Configurations</font></td>";
                                            echo "</tr>";
                                        //  echo "<tr>";
                                        //      echo "<td align=left width="10%">  &nbsp; <a href="javascript:void();" onclick="javascript:FileDownload('d:/webdata/tpmc/report/equip/EWS GRR Masterlist.xlsx');"><img border="0" src="".$grpnicon."xls.gif"></a></td>";     //closed requested by Audie
                                        //      echo "<td align=left width="90%"><font class=ft10 color=#000000>EWS GR&R Masterlist</font></td>";
                                        //  echo "</tr>";
                                            echo "<tr>";
                                                echo "<td align=left width="10%"> <a href="javascript:void();" onclick="window.open('http://sgewsweb.amk.st.com/webdata/tpmc/report/equip/Calibration Service Providers Certificates', '_blank')"><img border="0" src="".$grpnicon."service.gif"></a></td>";
                                                echo "<td align=left width="90%"><font class=ft10 color=#000000>CAL Service Providers Certificates</font></td>";//W:ReportequipCalibration Service Providers Certificates
                                            echo "</tr>";       
                                        
                                        
                                        if($badgeno == "018359" || $badgeno == "018432" || $badgeno == "016919" || $badgeno == "230933"){
                                            echo "<tr>";
                                                echo "<td align=left width="10%"> <a href="javascript:void();" onclick="Upload();"><img border="0" src="".$grpnicon."upload.jpg" width=40px height=40px></a></td>";
                                                echo "<td align=left width="90%"><font class=ft10 color=#000000>Upload RnR Report</font></td>";
                                            echo "</tr>";   
                                        }
                                            //end   
                                                                                
                                        echo "</table>";                            
                                    echo "</td>";
                                echo "</tr>";
                            echo "</table>";
                        echo "</td>";
                    echo "</tr>";
                echo "</table>";  
            echo "</div>";
      echo "<div id=tabs-6>"; include("tabProbSearch_filter.php"); echo "</div>";
      echo "<div id=tabs-7>"; include("probEquipProgram/tabProbEquip_filter.php"); echo "</div>";
        echo "</div>";
    echo "</div>";
echo "</form>";
echo "</body>";
echo "</html>";
?>

Below codes are JavaScript codes. Error line is under 4.1.

    /**
 * This array is used to remember mark status of rows in browse mode
 */
var marked_row = new Array;


/**
 * Sets/unsets the pointer and marker in browse mode
 *
 * @param   object    the table row
 * @param   interger  the row number
 * @param   string    the action calling this script (over, out or click)
 * @param   string    the default background color
 * @param   string    the color to use for mouseover
 * @param   string    the color to use for marking a row
 *
 * @return  boolean  whether pointer is set or not
 */
function setPointer(theRow, theRowNum, theAction, theDefaultColor, thePointerColor, theMarkColor)
{

    var theCells = null;

    // 1. Pointer and mark feature are disabled or the browser can't get the
    //    row -> exits
    if ((thePointerColor == '' && theMarkColor == '')
        || typeof(theRow.style) == 'undefined') {
        return false;
    }

    // 2. Gets the current row and exits if the browser can't get it
    if (typeof(document.getElementsByTagName) != 'undefined') {
        theCells = theRow.getElementsByTagName('td');
    }
    else if (typeof(theRow.cells) != 'undefined') {
        theCells = theRow.cells;
    }
    else {
        return false;
    }

    // 3. Gets the current color...
    var rowCellsCnt  = theCells.length;
    var domDetect    = null;
    var currentColor = null;
    var newColor     = null;
    // 3.1 ... with DOM compatible browsers except Opera that does not return
    //         valid values with "getAttribute"
    if (typeof(window.opera) == 'undefined'
        && typeof(theCells[0].getAttribute) != 'undefined') {
        currentColor = theCells[0].getAttribute('bgcolor');
        domDetect    = true;
    }
    // 3.2 ... with other browsers
    else {
        currentColor = theCells[0].style.backgroundColor;
        domDetect    = false;
    } // end 3

    // 4. Defines the new color
    // 4.1 Current color is the default one
    if (currentColor == ''
        || currentColor.toLowerCase() == theDefaultColor.toLowerCase()) {
        if (theAction == 'over' && thePointerColor != '') {
            newColor              = thePointerColor;
        }
        else if (theAction == 'click' && theMarkColor != '') {
            newColor              = theMarkColor;
        }
    }
    // 4.1.2 Current color is the pointer one
    else if (currentColor.toLowerCase() == thePointerColor.toLowerCase()
             && (typeof(marked_row[theRowNum]) == 'undefined' || !marked_row[theRowNum])) {
        if (theAction == 'out') {
            newColor              = theDefaultColor;
        }
        else if (theAction == 'click' && theMarkColor != '') {
            newColor              = theMarkColor;
            marked_row[theRowNum] = true;
        }
    }
    // 4.1.3 Current color is the marker one
    else if (currentColor.toLowerCase() == theMarkColor.toLowerCase()) {
        if (theAction == 'click') {
            newColor              = (thePointerColor != '')
                                  ? thePointerColor
                                  : theDefaultColor;
            marked_row[theRowNum] = (typeof(marked_row[theRowNum]) == 'undefined' || !marked_row[theRowNum])
                                  ? true
                                  : null;
        }
    } // end 4

    // 5. Sets the new color...
    if (newColor) {
        var c = null;
        // 5.1 ... with DOM compatible browsers except Opera
        if (domDetect) {
            for (c = 0; c < rowCellsCnt; c++) {
                theCells[c].setAttribute('bgcolor', newColor, 0);
            } // end for
        }
        // 5.2 ... with other browsers
        else {
            for (c = 0; c < rowCellsCnt; c++) {
                theCells[c].style.backgroundColor = newColor;
            }
        }
    } // end 5

    return true;
} // end of the 'setPointer()' function