On iPad it is possible that the timer set in touchStart() will not ha…

…ve yet fired and that touchEnd() will come in in the same Run Loop as the one that started with the call to touchStart(). The bad thing that happens is that even though we cleared this.touch, occasionally if touchEnd() comes in right at the end of the Run Loop and then the timer expires and starts a new Run Loop to call beginTouchesInContent(), that this.touch will STILL exist here. There's no explanation for it, and it's not 100% reproducible, but there is about a 40ms window where the firing timer and the end touch cause a crash. What happens is that if we try to capture the touch that has already ended, assignTouch() in RootResponder will check touch.hasEnded and throw an exception.

frameworks/desktop/views/scroll.js

@@ -1095,7 +1095,16 @@ SC.ScrollView = SC.View.extend({
     if (gen !== this.touchGeneration) return;
 
     var touch = this.touch, itemView;
-    if (touch && this.tracking && !this.dragging && !touch.touch.scrollHasEnded) {
+
+    // NOTE!  On iPad it is possible that the timer set in touchStart() will not have yet fired and that touchEnd() will
+    // come in in the same Run Loop as the one that started with the call to touchStart().  The bad thing that happens is that 
+    // even though we cleared this.touch, occasionally if touchEnd() comes in right at the end of the Run Loop and
+    // then the timer expires and starts a new Run Loop to call beginTouchesInContent(), that this.touch will STILL exist
+    // here.  There's no explanation for it, and it's not 100% reproducible, but what happens is that if we try to capture
+    // the touch that has already ended, assignTouch() in RootResponder will check touch.hasEnded and throw an exception.
+
+    // Therefore, don't capture a touch if the touch still exists and hasEnded
+    if (touch && this.tracking && !this.dragging && !touch.touch.scrollHasEnded && !touch.touch.hasEnded) {
       // try to capture the touch
       touch.touch.captureTouch(this, YES);