How to trap for nothing

Hi all-

I have a very simple text field (textInput component instance)

I'm trying to trap when a user doesn't enter anything in the field. In my function I've tried trapping for NULL, "NULL", undefined, etc. but can't seem to get a condition that works for my if statement:

ex: if (userTicket_txt.text =NULL){...};

My condition never yields true with what I've tried. I'm sure it's something simple but I'm still scratching my head.... anyone have any ideas?

Thanks in advance-

rich