Allow direct updates to the paint object without prior validation.
The verification process is deemed inefficient;
users are expected to ensure the paint is updated using a canvas
that contains it.
This might break the backward compatibility.
dispose of the resources at the end of the paint deletion.
This will help retain the resources of the retained paints
and reuse them after reconstructing the next scene.
This correction ensures a consistent use of 'ref' and 'unref' for paints to release memory properly.
The memory leak occurred when a picture was not pushed to a valid canvas.
This issue was reported by the unit-test memory sanitizer.
