TrackPerson inserting with interpolation not working as expected

When inserting a frame to the TrackPerson with missing frames in between, the expected behaviour, is that the points inbetween will be interpolated.
But this is not happening!

To reproduce:

• Create TrackPerson p with point at frame 0.
• p.insertAtFrame(10, someOtherPoint, _nr, false) (_nr can be set however you like, false: do not extrapolate)

Expected Behaviour:

• p.trackPointExists(frame) == true for all frames from 0 to 10

Real Behaviour:

• fail at p.trackPointExists(7) -> So in total 4 missing trackpoints!

I will commit a failing testcase on a branch for this issue.