"Use internal icon set" for button icons causes DOpus to crash

When creating a button, giving it an icon from an external icon file works as expected. However, trying to select one from the internal icon set cause DOpus to crash every time. Sounds like maybe the iconset file is corrupt but I don't wish to delete it if that means losing a few custom icons I've saved therein. What's the solution?

The internal icon set is built into the program so if it was corrupted the program would detect it and warn you.

If Opus crashes, a log should be created. Can you send it to us if so? See Automatic crash logs (for bug reports) for details of how to find it.