fix detecting video on plex (#434)

inject.js

@@ -206,7 +206,6 @@
       var fragment = document.createDocumentFragment();
       fragment.appendChild(wrapper);
 
-      this.video.classList.add('vsc-initialized');
       this.video.dataset['vscid'] = this.id;
 
       switch (true) {
@@ -342,13 +341,12 @@
           if (added) {
             new tc.videoController(node, parent);
           } else {
-            if (node.classList.contains('vsc-initialized')) {
             let id = node.dataset['vscid'];
+            if (id) {
               let ctrl = document.querySelector(`div[data-vscid="${id}"]`)
               if (ctrl) {
                 ctrl.remove();
               }
-              node.classList.remove('vsc-initialized');
               delete node.dataset['vscid'];
             }
           }