Cannot set properties of null but the item exists HTML JavaScript

I'm adding titles to existing divs. I'm using Visual Studio's Live Server and it works perfectly but when I upload it on Netlify it gives me "null" error. I can't figure out why is it doing that. Here's the part of the code where's the error:

while (suratebiNames < 398) {
    var img = document.getElementById("meme" + suratebiNames);
    img["title"] = text.split("\n")[suratebiNames].toLowerCase();
    suratebiNames++;
}