Describe the bug

I've tried dragging Composite Association to BDD graph. Operation failed and 'unexpected error, please report' window showed up.

To Reproduce

Steps to reproduce the behavior:

1. Create new Block Definition Diagram
2. Drag Composite Association into workspace.

Error report from tools:
note.txt

Expected behavior

Composite Association should appear normally.

Screenshots

OS

• Linux - Ubuntu 24.04.2 LTS
• macOS
• Windows

Version

Version of Gaphor: 3.1.0

Additional information

The same happens for different relation arrows, connector and flow arrows.
The same happens at least in some other types of diagrams (I didn't check all of them - I don't think it's a problem with them).
If I try to copy-paste relation arrow created in older version it works normally.