fix(tap): only check classList on tap target if it has classList

Closes #1677

Author: ajoslin

Diff for: js/utils/tap.js

@@ -530,7 +530,10 @@ function tapHasPointerMoved(endEvent) {
   }
   var endCoordinates = getPointerCoordinates(endEvent);
 
-  var releaseTolerance = (endEvent.target.classList.contains('button') ? TAP_RELEASE_BUTTON_TOLERANCE : TAP_RELEASE_TOLERANCE);
+  var hasClassList = endEvent.target.classList && endEvent.target.classList.contains;
+  var releaseTolerance = hasClassList & endEvent.target.classList.contains('button') ?
+    TAP_RELEASE_BUTTON_TOLERANCE :
+    TAP_RELEASE_TOLERANCE;
 
   return Math.abs(tapPointerStart.x - endCoordinates.x) > releaseTolerance ||
          Math.abs(tapPointerStart.y - endCoordinates.y) > releaseTolerance;