Dispatcher: Do not propagate over removed nodes

Fixes gh-326
Closes gh-339

src/dispatcher.js

@@ -318,6 +318,10 @@ var dispatcher = {
     while (target !== document && !target.contains(event.relatedTarget)) {
       targets.push(target);
       target = target.parentNode;
+      // Touch: Do not propagate if node is detached.
+      if (!target) {
+        return;
+      }
     }
     if (propagateDown) {
       targets.reverse();