Expected an empty string to return false in Javascript

I am trying to solve the CodeWars code challenge The Hashtag Generator
:

The marketing team is spending way too much time typing in hashtags.
Let’s help them with our own Hashtag Generator!

Here’s the deal:

• It must start with a hashtag (#).
• All words must have their first letter capitalized.
• If the final result is longer than 140 chars it must return false.
• If the input or the result is an empty string it must return false.

Examples

" Hello there thanks for trying my Kata"  =>  "#HelloThereThanksForTryingMyKata"
"    Hello     World   "                  =>  "#HelloWorld"
""                                        =>  false

This is my code:

function generateHashtag (str) {
   if (str == "") {return false;}
   else
     {
      let text = str.trim();
      const myArray = text.split(" ");
      let mot ="";
      let finalStr = ""
      for(let i=0; i< myArray.length; i++)
        {
          mot = myArray[i];
          mot = mot.charAt(0).toUpperCase() + mot.slice(1);
          finalStr =finalStr + mot;
        }
      if(finalStr.length >140){return false;}
      else {return "#"+finalStr;}
    }
}

This is the error I got:

Expected an empty string to return false: expected ‘#’ to equal false

I don’t understand why I get this error, as I have included the empty string check.