fixed #544:

lib/fastclick.js

@@ -22,6 +22,7 @@
 	 */
 	function FastClick(layer, options) {
 		var oldOnClick;
+		var oldOnClickNoop = function () {};
 
 		options = options || {};
 
@@ -167,9 +168,11 @@
 			// - the old one won't work if passed to addEventListener directly.
 			oldOnClick = layer.onclick;
 			layer.addEventListener('click', function(event) {
-				oldOnClick(event);
+				if (layer.onclick === oldOnClickNoop) {
+					oldOnClick(event);
+				}
 			}, false);
-			layer.onclick = null;
+			layer.onclick = oldOnClickNoop;
 		}
 	}