This case is a copy of case 1338752 in Fogbugz, and this was created just so that we can have backport in the new system.
Reproduction steps:
1. Open the attached "TestLanguageCrash.zip" project
2. Go to Preferences -> Languages -> Editor Language
3. Select any other Language, wait for the Editor to load
4. Select any language besides the currently selected one
5. Click on the Menu Bar
Expected result: Menu Bar selection list shows up
Actual result: Editor crashes
Reproducible with: 2019.3.0a6, 2019.4.27f1, 2020.3.11f1, 2021.1.9f1, 2021.2.0a17
Not reproducible with: 2018.4.35f1, 2019.3.0a5
Could not test with: 2021.2.0a18 (wasn't able to download Languages packs)
Stack trace:
#0 0x0000010b45b41e in -[CocoaMainMenu validateMenuItem:]
#1 0x007fff22f5480a in -[NSMenu _enableItem:]
#2 0x007fff230a1b93 in -[NSCarbonMenuImpl _carbonUpdateStatusEvent:handlerCallRef:]
#3 0x007fff23087fb9 in NSSLMMenuEventHandler
#4 0x007fff287c2400 in DispatchEventToHandlers(EventTargetRec*, OpaqueEventRef*, HandlerCallRec*)
#5 0x007fff287c17d9 in SendEventToEventTargetInternal(OpaqueEventRef*, OpaqueEventTargetRef*, HandlerCallRec*)