No Median for Empty Data in Enforce Rigid Bones

[philipqueen]

I ran into the following error while trying to process a recording with only hand data (one hand). It appears we need to better handle the median calculation in the case of empty data.

:MainProcess TID:11891798016:Dummy-7 ] Failed during `enforce rigid bones`, error: `no median for empty data`
[2024-10-03T23:42:49.533538] [Δt:0.000121s] [   DEBUG] [root] [run_ajc_addon_main:run_ajc_blender_addon_subprocess():94] [PID:91266:MainProcess TID:11891798016:Dummy-7 ] no median for empty data

I'll get to this when I have some time, but someone else feel free to tackle it if you'd like!

Steps to Reproduce:

• Record a multi camera recording with just a hand in it
• Process recording through Freemocap
• Try exporting to Blender

[jonmatthis]

I'll sweep this up in the PR reviews I'm working on now