fix(FEC-12527): turning on hls debug mode in config causes the player…

… to crash (#176)

In some cases hls.js triggers our event handlers (specifically _onAudioTrackSwitched) before the _onManifestLoaded handler. When _onAudioTracksSwitched calls _playerTracks.find, which is undefined, it crashes.
The solution is to initialize _playerTracks with an empty array before _onManifestLoaded fills it with the real values.

src/hls-adapter.js

@@ -112,7 +112,7 @@ export default class HlsAdapter extends BaseMediaSourceAdapter {
    * @type {Array<Track>}
    * @private
    */
-  _playerTracks: Array<Track>;
+  _playerTracks: Array<Track> = [];
   /**
    * stream start time in seconds
    * @type {?number}