Fix NullPointerException on double tap on hold.

We don't need to confirm that pointers are non-zero in TouchExplorer#onDoubleTapAndHold; it is the job of the gesture matcher and the gesture manifold to prevent weirdness.
Bug: 146997332
Test: atest AccessibilityGestureDetectorTest TouchExplorerTest GestureManifoldTest
Change-Id: I12eb42155c1e55b13840bacea962be4759354214
2 files changed