Okay - I'm still not really sure what you need GM Link to do. Do you want it to be able to import Tile Set assets into GameMaker? The error you linked comes from the other extension, so it doesn't help me that much unless I really start digging. It could also be that the issue lies with that extension and not GM Link. Feel free to drop me any more information you have about this as well as how you reproduce that error, and I'll see if I can find some time to look at it. I cannot promise you it'll be soon.
Thanks for the reply! Yes, I want to import tile assets to GameMaker. The error shows up ONLY when I have both GM Link and GMS2 Autotile Converter in my Asesprite files. Alone they both work perfectly fine. Honestly I'm a complete stranger to Lua and mostly programming in general, so I'm not sure what info to provide. You can take your time! Importing them manually work for now :-)