The pad is not empty after clearOnDoubleClick

[ClementHard]

After using the clearOnDoubleClick feature, the pad is not empty (isEmpty() == false).
I want to use the OnSignedListener to toggle a button state but onSigned is always called after the double click gesture.

If you look at this line, you can see that something is drawn after MotionEvent.ACTION_UP events preventing the pad to be cleared properly.

[Mauker1]

I've made a PR to fix this. As you can see on #91