The right mouse button (which is the "Use" button for throwing gems etc.)
function sets the Button B flag in the _buttons flag field, but never
cleared it. This resulted in blocking of setting of movement waypoints
with the left button and thus locked up the player character.
You could avoid this by using the "Return" key which is also mapped to
use, but this would only be possible on desktop ports or with a virtual
keyboard.
This commit fixes the mouse handling code to clear the flag and thus
avoids future bug reports.
d7972603e7