Crash when push fails.

[AndrejSlo]

Steps to Reproduce:

1. Commit & Push - commit succeeds but if push fails for any reason
2. Create a new branch to preserve changes
3. Check out the origin branch - SourceGit crashes

Notes:

• This crash is 100% reproducible.
• After restarting SourceGit, everything works normally again.
• SourceGit v2026.18