Massively refactored the code so that it is much more maintainable. A big thank you to Chuck for helping me out.

Fixed: Errors.

Apparently, refactoring the modData functionality into a function caused it to fail. This has been fixed, apologies for the severe lag and error spam.

Refactored: EnsureModRunsOnlyOnce method added
Added: NullReference check for buildingDef.

The code runs once and only once. If you use this on an existing save when you are outside, it will give an error if you are not inside a building. This has been fixed.