Changing the Articulation Joint Type from Revolute to Fixed throws IndexOutOfRangeException errors in Console and jams the Robotic Arm.
Refer to the attached Video.

Steps to Reproduce:
1. Open Attached Project
2. Open 'Articulation Robot' Scene
3. Hierarchy > Base/Shoulder/Elbow/Wrist/HandE > Inspector > Articulation Body > Joint Type > Fixed
4. Enter Play Mode
5. Controls - WA,SD,OP,KL,NM,VB,ZX (Depending on the part of the Arm changed)

Actual Result:
IndexOutOfRangeException errors in Console

Expected Result:
No errors in the console and the Arm functions smoothly

Note:
The Feature to Connect Articulation bodies to Regular Joints was introduced in 2020.2.0a15

Reproducible with:
2020.2.0a15

Environment:
Windows 10 only

License type: Pro