Fix problems with load-subtitles shortcut and iframed video elements

- Removed short-circuit that prevents child iframe video-select-dialog
  listeners from receiving commands.
- But if we do this then any iframe without video elements can show the
  'no video elements' dialog on any 'load-subtitles' command.
- So we just remove the 'no video elements' entirely. This restores the
  behavior from the latest released version of the extension.

extension/src/controllers/video-select-controller.ts

@@ -37,10 +37,6 @@ export default class VideoSelectController {
     }
 
     bind() {
-        if (window.self !== window.top) {
-            return;
-        }
-
         this.messageListener = (
             request: any,
             sender: chrome.runtime.MessageSender,
@@ -92,8 +88,6 @@ export default class VideoSelectController {
         } else if (this._bindings.length > 1) {
             // Toggle on
             this._showUi(openedFromMiningCommand);
-        } else {
-            this._showNoVideoElementsUi();
         }
     }
 
@@ -122,12 +116,6 @@ export default class VideoSelectController {
         client.updateState({ open: true, themeType, videoElements, openedFromMiningCommand });
     }
 
-    private async _showNoVideoElementsUi() {
-        const client = await this._prepareAndShowFrame();
-        const themeType = await this._settings.getSingle('themeType');
-        client.updateState({ open: true, themeType, videoElements: [] });
-    }
-
     private async _prepareAndShowFrame() {
         this._frame.language = await this._settings.getSingle('language');
         const isNewClient = await this._frame.bind();