Make sure to send HOVER_EXIT when starting touch exploration if we haven't sent it already.

Fix: 290719741
Test: Manual. Repeatedly interrupt and continue touch exploration to trigger sending ACTION_HOVER_ENTER. This would previously cause a crash.
Change-Id: I7c35172c82c29289cac565a704bc5d4fbd579773

services/accessibility/java/com/android/server/accessibility/gestures/TouchExplorer.java

@@ -1341,6 +1341,8 @@ public class TouchExplorer extends BaseEventStreamTransformation
                 Slog.e(LOG_TAG, "Unable to find a valid pointer for touch exploration.");
                 return;
             }
+            // Send hover exit if we haven't closed a previous touch exploration event stream.
+            sendHoverExitAndTouchExplorationGestureEndIfNeeded(pointerId);
             final int pointerIdBits = (1 << pointerId);
             final int policyFlags = mState.getLastReceivedPolicyFlags();
             mSendHoverEnterAndMoveDelayed.setPointerIdBits(pointerIdBits);