[Bug]: null pointer exception when using campaign properties editor window

[Baaaaaz]

Describe the Bug

Getting java.lang.NullPointerException when trying to change campaign properties using the editor window

Originally raised in Discord: https://discord.com/channels/296230822262865920/1406931085606260736

To Reproduce

From Discord user:

Open a new campaign
Edit -> Campaign Properties
Highlight Basic token type
Highlight any default value cell
Click the three dots to open an editor window
Click ok to close the window (This can be blank or have anything typed in it)
Error appears

Expected Behaviour

No null pointer exception when using campaign properties editor window

Screenshots

MapTool Info

1.18.3

Desktop

Win11

Additional Context

From Discord user:

I tested this on my previous maptool install (17.1) and the error does not appear when I follow those steps. Also uninstalled and reinstalled 18.3 and I get the same issue.

If I don't open the editor window and just type in the cell, I can change the default property with no error.

[kwvanderlinde]

Stems from #5369