[zeditor] White combo select square scrolls past bottom of combo lists

[Asuna Yuuki Nagato]

Steps to recreate:


Set drawing mode to pool, auto, or alias
Scroll down in the rightmost combo list a bit
Click a combo in the bottommost visible row of that combo list
Slowly scroll back up to the top of the combo list
Observe selection square goes past bottom of combo list

[Asuna Yuuki Nagato]

In Pool drawing mode, the square is drawn by the call to safe_rect right before the //Handle Preview comment