The problem is caused because you must have either made or downloaded a customization file for that airport which was made with a very early version of GSX L2, that had a small bug in the automatic jetway logo selection, since it was trying to call a non-existent logo for Aerogate ( it called it ARGT, which is the internal code ), instead of AEROGATE, which is the correct name of that logo and what is being saved if you select Aerogate in the editor in the current version. The bug has been fixed a couple of days after GSX L2 was released, so your file must have been made before that time.
You might be able to save that file by replacing all strings that reads _ARGT with _AEROGATE in the file.
Or, if you don't care about it (I'm sure you'll find better and more updated versions in the forum), just remove it, it's the file named:
%APPDATA%\Virtuali\GSX\eddm-sssirf.ini