ArmorPaint crashes when saving anything

ArmorPaint
1

I’m using the following version: v1.0 alpha (2024-02-01) - Linux - OpenGL.
When I’m trying to save a work as an .arm file I get the following error:

Trace: TypeError: Cannot read properties of null (reading 'constructor')
    at ArmPack.writeDummy (<anonymous>:1573:16)
    at ArmPack.writeObjectDummy (<anonymous>:1620:17)
    at ArmPack.writeDummy (<anonymous>:1609:17)
    at ArmPack.encode (<anonymous>:1451:13)
    at ExportArm.runProject (<anonymous>:13400:26)
    at _init (<anonymous>:12109:19)
    at App.update (<anonymous>:1202:21)
    at App.render (<anonymous>:1237:9)
    at System.renderCallback (<anonymous>:5482:9)