Check handling of "frames" in apply_motion_field()

[jonasfbraun]

We might have to rework how this function deals with "frames" because it includes inherent assumptions.
The way this function is used right now is fine (only in motion_compensate()), but I tried using it outside of ofco and it does not do what would be expected if you want to only apply it to range of frames that does not start from frame 0