Codeigniter A PHP Error was encountered – Trying to access array offset on value of type null

A PHP Error was encountered
Severity: Notice

Message: Trying to access array offset on value of type null

Filename: helpers/common_helper.php

Line Number: 35

Backtrace:

File: F:xampphtdocssdpnew1applicationhelperscommon_helper.php
Line: 35
Function: _error_handler

File: F:xampphtdocssdpnew1applicationcontrollersadminUsers.php
Line: 36
Function: get_admin_name

File: F:xampphtdocssdpnew1index.php
Line: 315
Function: require_once

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
// -----------------------------------------------------------------------------
// Get Language by ID
function get_lang_name_by_id($id)
{
    $ci = & get_instance();
    $ci->db->where('id',$id);
    return $ci->db->get('ci_language')->row_array()['name'];
}

// -----------------------------------------------------------------------------
// Get Language Short Code
function get_lang_short_code($id)
{
    $ci = & get_instance();
    $ci->db->where('id',$id);
    return $ci->db->get('ci_language')->row_array()['short_name'];
}

// -----------------------------------------------------------------------------
// Get Language List
function get_language_list()
{
    $ci = & get_instance();
    $ci->db->where('status',1);
    return $ci->db->get('ci_language')->result_array();
}

// -----------------------------------------------------------------------------
// Get Admin name by ID
function get_admin_name($id)
{
    $ci = & get_instance();
    $ci->db->where('user_id',$id);
    $ret = $ci->db->get('ci_users')->row_array()['username']; // Problem area 
    if($ret === null || trim($ret) === '') //DH in case of the 'creator' has been deleted
        return 'Unknown';
    return $ret;
}

// -----------------------------------------------------------------------------
// Get country list
function get_country_list()
{
    $ci = & get_instance();
    return $ci->db->get('ci_countries')->result_array();
}

// -----------------------------------------------------------------------------
// Get country name by ID
function get_country_name($id)
{
    $ci = & get_instance();
    return $ci->db->get_where('ci_countries', array('id' => $id))->row_array()['name'];
}

// -----------------------------------------------------------------------------
// Get City ID by Name
function get_country_id($title)
{
    $ci = & get_instance();
    return $ci->db->get_where('ci_countries', array('slug' => $title))->row_array()['id'];
}

// -----------------------------------------------------------------------------
// Get country slug
function get_country_slug($id)
{
    $ci = & get_instance();
    return $ci->db->get_where('ci_countries', array('id' => $id))->row_array()['slug'];
}

// -----------------------------------------------------------------------------
// Get country's states
function get_country_states($country_id)
{
    $ci = & get_instance();
    return $ci->db->select('*')->where('country_id',$country_id)->get('ci_states')->result_array();
}

// -----------------------------------------------------------------------------
// Get state's cities
function get_state_cities($state_id)
{
    $ci = & get_instance();
    return $ci->db->select('*')->where('state_id',$state_id)->get('ci_cities')->result_array();
}

// Get state name by ID
function get_state_name($id)
{
    $ci = & get_instance();
    return $ci->db->get_where('ci_states', array('id' => $id))->row_array()['name'];
}

// -----------------------------------------------------------------------------
// Get city name by ID
function get_city_name($id)
{
    $ci = & get_instance();
    return $ci->db->get_where('ci_cities', array('id' => $id))->row_array()['name'];
}

// -----------------------------------------------------------------------------
// Get city ID by title
function get_city_slug($id)
{
    $ci = & get_instance();
    return $ci->db->get_where('ci_cities', array('id' => $id))->row_array()['slug'];
}

/**
 * Generic function which returns the translation of input label in currently loaded language of user
 * @param $string
 * @return mixed
 */
function trans($string) //DH modif
{
    $ci =& get_instance();
    // return $ci->lang->line($string); //DH : original line

    $tmp = $ci->lang->line($string);
    if( !empty($tmp) )
        return $tmp;
    return '!'. $string . '!';
}