* Made it impossible to try to calculate/create new motion paths lasting 0
frames (i.e. 250 to 250) since we cannot allocate a zero-length array for these.
Start frame can now be at most end-frame - 1, and end frame at least start frame
+ 1
* If an invalid configuration does occur, warnings/reports will now be issued in
response to this instead of silently failing (as per this bugreport).
8da2812100