This function returns the name of the next file that satisfies
the previously given mask and the attributes (defined by file_find_first). If no such
file exists, the empty string is returned.
WARNING! This function may not work as you expect due to GameMaker: Studio being sandboxed! Please see the section on File System Limits for more information.
NOTE: This function works on all the C++ target platforms (Windows, Mac, iOS, Android and WinPhone), BUT the filter flags only work on Windows and WinPhone.
file = file_find_next();
This will return the next file that matches the previously given attributes.