Crash when modifying GameMaker 2.3+ rooms

[nickavv]

The application crashes when you try to save a GameMaker 2.3 room. The data loads just fine so the 2.2 and 2.3 rooms aren't totally incompatible, but something about the format must have changed from 2.2 to 2.3. Need to run in VS so I can look at the stack trace and identify the problem.