For one, paintcurves were not considered in curves sculpt mode at all
(so you couldnt draw them). This is now enabled.
And the second issue was that since curves sculpt mode uses the reguar
paint_stroke_modal() [which handles paintcurves], this was actually
excuted, freeing the PaintStroke from SculptCurvesBrushStrokeData (but
not the CurvesSculptStrokeOperation) and immediately return
OPERATOR_FINISHED from modal (resulting in a double MEM_delete of
SculptCurvesBrushStrokeData -- in both invoke and modal).
There might be better ways to handle the memory free, for now the double
freeing is prevented by setting the operator customdata to NULL (and
check for that later).
Maniphest Tasks: T101062
Differential Revision: https://developer.blender.org/D16099
3f91540cef