When requesting quickly a change in the quality of a video, the

HTMLVideoElement wasn't always ready and thus null. We tried to remove
some EventListener of something null, so it crashed. It is not the case
anymore, as a check on the HTMLVideoElement (either null or undefined)
is done.

Author: aberthet-gpsw

src/display/video/VideoHTML5.js

@@ -1540,20 +1540,26 @@ FORGE.VideoHTML5.prototype._clearRequestedVideo = function()
     {
         //Remove all listeners used for the requested video
         var element = video.element;
-        element.removeEventListener("loadstart", this._onRequestLoadStartBind, false);
-        element.removeEventListener("loadedmetadata", this._onRequestLoadedMetaDataBind, false);
-        element.removeEventListener("loadeddata", this._onRequestLoadedDataBind, false);
-        element.removeEventListener("play", this._onRequestCanPlayBeforeSeekBind, false);
-        element.removeEventListener("seeked", this._onRequestSeekedBind, false);
-        if (FORGE.Device.edge === true || FORGE.Device.ie === true)
-        {
-            element.removeEventListener("canplaythrough", this._onRequestCanPlayAfterSeekBind, false);
-        }
-        else
+
+        if (typeof element !== "undefined" && element !== null)
         {
-            element.removeEventListener("canplay", this._onRequestCanPlayAfterSeekBind, false);
+            element.removeEventListener("loadstart", this._onRequestLoadStartBind, false);
+            element.removeEventListener("loadedmetadata", this._onRequestLoadedMetaDataBind, false);
+            element.removeEventListener("loadeddata", this._onRequestLoadedDataBind, false);
+            element.removeEventListener("play", this._onRequestCanPlayBeforeSeekBind, false);
+            element.removeEventListener("seeked", this._onRequestSeekedBind, false);
+
+            if (FORGE.Device.edge === true || FORGE.Device.ie === true)
+            {
+                element.removeEventListener("canplaythrough", this._onRequestCanPlayAfterSeekBind, false);
+            }
+            else
+            {
+                element.removeEventListener("canplay", this._onRequestCanPlayAfterSeekBind, false);
+            }
+
+            element.removeEventListener("error", this._onRequestErrorBind, false);
         }
-        element.removeEventListener("error", this._onRequestErrorBind, false);
 
         //Destroy the requested video
         this._destroyVideo(video);