setloop fails to constrain window size parameter when playback is reversed

[Lluiser]

steps to replicate bug:

~ set window position and size large enough that the playhead loops around to the beginning of the loop
~ set speed to negative (reverse)
~ use the setloop command to loop an area not at the beginning

expected behaviour: when playhead reaches 0 as defined by the new setloop, it jumps to the end of the loop and continues playing backwards
actual result: the playhead ignores the leftmost setloop boundary and continues playing backwards all the way to the beginning of the buffer before looping