Merge branch '428-on-touch-device-clicking-on-molart-bar-causes-js-error' into 'master'

Resolve "on touch device clicking on molart bar causes JS error"

Closes #428

See merge request minerva/core!322

frontend-js/src/main/js/GuiConnector.js

@@ -69,10 +69,14 @@ GuiConnector.prototype.init = function () {
   });
 
   self._touchStartEvent = function (e) {
-    self.updateMouseCoordinates(e.originalEvent.touches[0].pageX, e.originalEvent.touches[0].pageY);
+    if (e.originalEvent !== undefined) {
+      self.updateMouseCoordinates(e.originalEvent.touches[0].pageX, e.originalEvent.touches[0].pageY);
+    }
   };
   self._touchMoveEvent = function (e) {
-    self.updateMouseCoordinates(e.originalEvent.touches[0].pageX, e.originalEvent.touches[0].pageY);
+    if (e.originalEvent !== undefined) {
+      self.updateMouseCoordinates(e.originalEvent.touches[0].pageX, e.originalEvent.touches[0].pageY);
+    }
   };
 
   // force browser to update mouse coordinates whenever mouse move