with mouse crashes blender.
Issue here is that paint operator invocation, immediately calls modal,
which checks if event is the same as initialization event plus keyup.
Since using the mouse on amenu calls the operator on mouse button up,
the operator ended immediately and that cause immediate cleanup and
crash,
Worked around this by forbidding the operator to finish on first modal
call (which is expected by all the asserts on invoke anyway). This
prevents the crash but requires an extra up event to end.
Also, ported part of Jason Wilkins' patch to stroke code to allow for
stroke sampling to be done before a dab is first performed and as soon
as the stroke begins
1c314aae73