Crash when adding virtual bones

[AchimTuran]

Describe the bug
Adding virtual bones for a skeleton with existing anim sequences crash the editor.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. Windows]
• Version [e.g. v0.4]

Additional context
Add any other context about the problem here.

[NxRoot]

If you SHIFT+Click the option you can customize the script, just remove the "Recompress Animations" node from the function then save and close.

1. Now right-click the skeleton and select "Add Unweighted Bones".
2. Then right-click the skeleton and select "Recompress Animations". (The engine will crash but that's ideal)

This way you can still call the recompress animations but manually.