call_user_func_array() expects parameter 1 to be a valid callback, function

here is the full message:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘az_enqueue_color_picker’ not found or invalid function name in /home/nutrun/public_html/wp-includes/class-wp-hook.php on line 298

I noticed that error message after the programmer used some sort of back up restore software.

He tells me that this error message is with wordpress and he never touched the codes in wordpress. I need to know how to fix this before we launch and what could have caused it.

Anyone has any idea? I search www.ads-software.com and Google, but no one seem to have encountered that before.

Note: I’m not a programmer, but I’ve been in the Internet marketing field for 14 years. I do understand CSS and HTML. But not actual programming.

Thanks