jQuery Ajax small fix

I have a function that makes an ajax call every 4 seconds but on some cases this is a overkill for the server because the 1st ajax request still hasn't returned while the script sends a 2nd ajax request. This keeps piling up and it slows down the site until it starts having errors and issues.

We have to run a check to not send a next ajax request unless the previous one has returned successfully.

This should be a small and quick fix for anyone who knows what he is doing.