Steps to reproduce:
1. Open the “user’s attached project”
2. Open “SampleScene”
3. Make some changes to the project
4. Enter Play Mode
5. Press command + S to save while Play Mode is loading
6. Observe crash

Reproducible with versions: 6000.0.13f1, 6000.0.28f1, 6000.1.0a4
Not reproducible with versions: 2021.3.46f1, 2022.3.53f1, 6000.0.12f1
Fixed in version: 6000.1.0a5

Reproducible on: macOS 15.1 (M1 Max), macOS 14.6.1 (Intel)
Not reproducible on: Windows 11

First few lines of StackTrace:
{noformat}
#0 0x00000189d072a0 in -[NSApplication endModalSession:]
#1 0x000001079b30c0 in -[ProgressbarController hideWindow]
#2 0x000001079b3b20 in -[ProgressbarNotificationHandler handleClearNotification:]
#3 0x00000185f46f80 in __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__
#4 0x00000185fd8274 in ___CFXRegistrationPost_block_invoke{noformat}