fix issue where video player renders twice (TNL-3064)

common/lib/xmodule/xmodule/js/src/video/01_initialize.js

@@ -596,7 +596,11 @@ function (VideoPlayer, i18n) {
                     '[Video info]: YouTube returned an error for ' +
                     'video with id "' + self.id + '".'
                 );
-                self.loadHtmlPlayer();
+                // If the video is already loaded in `_waitForYoutubeApi` by the
+                // time we get here, then we shouldn't load it again.
+                if (!self.htmlPlayerLoaded) {
+                    self.loadHtmlPlayer();
+                }
             });
 
             window.Video.loadYouTubeIFrameAPI(scriptTag);