fix(pinning): bind the callback for contact list clicking

modules/UI/videolayout/VideoLayout.js

         // the local video thumb maybe one pixel
         this.resizeThumbnails(false, true);
 
+        this._onContactClicked = onContactClicked.bind(this);
+
         this.registerListeners();
     },
 
     registerListeners() {
         eventEmitter.addListener(UIEvents.LOCAL_FLIPX_CHANGED,
             onLocalFlipXChanged);
-        eventEmitter.addListener(UIEvents.CONTACT_CLICKED, onContactClicked);
+        eventEmitter.addListener(UIEvents.CONTACT_CLICKED,
+            this._onContactClicked);
     },
 
     /**
      * @returns {void}
      */
     unregisterListeners() {
-        eventEmitter.removeListener(UIEvents.CONTACT_CLICKED, onContactClicked);
+        if (this._onContactClicked) {
+            eventEmitter.removeListener(UIEvents.CONTACT_CLICKED,
+                this._onContactClicked);
+        }
     },
 
     initLargeVideo () {