regEx wp core file

I was able to answer my own question.
Simply adding a 0-9 into the code above remedied the situation.

Here is the final code:

if (!name || !/^[a-z0-9][a-z0-9\-\_:\.]*$/i.test(name)) {
    tinyMCEPopup.alert('advanced_dlg.anchor_invalid');
    return;
}