can't save. Lost progress :(

[Shpungo]

[Window Title]
Error

[Main Instruction]
An internal error occured:

[Content]
referencing a nonexistant file
Please save your work (use 'save as' to so you don't overwrite things)
and restart Magic Set Editor.

You should leave a bug report on https://github.com/twanvl/MagicSetEditor2/issues/
Press Ctrl+C to copy this message to the clipboard.

Call stack:
[00] 00007FF63FCB9987
[01] 00007FF63FCBD986
[02] 00007FF63FCBDF44
[03] 00007FF63FCCD6A8
[04] 00007FF63FAFA5AC
[05] 00007FF63FB34D07
[06] 00007FF63FB7077A
[07] 00007FF63FB723A7
[08] 00007FF63FCC2352
[09] 00007FF63FCC0594
[10] 00007FF63FC1DC77
[11] 00007FF63FC58A8C
[12] 00007FF63FEAB644
[13] 00007FF63FEDE1FF
[14] 00007FF63FEDDE77
[15] 00007FF63FEDF04C
[16] 00007FF63FEDE12A
[17] 00007FF63FD3D43E
[18] 00007FF63FEDE17C
[19] 00007FF63FEDEC3A
[20] 00007FF63FD9BF46

[OK]