UTMT throws an exception when trying to save data with new tiles

[Senjay-id]

Describe the bug

When trying to save the data with tiles being added using a script it throws an error The layer tile isn't even added to the room

Reproducing steps

1. Open the data.win and run the attached script file inside utmt script.zip

2. Save the data

Setup Details

1. Latest bleeding edge
2. Windows 10 Latest
3. ZERO Sievert