fix(FEC-11655): System highlights 2 options (captions) after clicking…

… the "Change media" button on Safari (#612)

Description of the Changes
issue: look at _getParsedTextTracks() on https://github.com/kaltura/playkit-js/blob/master/src/engines/html5/media-source/adapters/native-adapter.js#L696
when this method called at the second time (like after calling changeMedie() in this case) the textTracks including the external text trcak.

and the first condition evaluates to false and therefore the indexes start from 1 instead of 0 which leads to an incorrect index value (that is - same index for two different tracks) on the getExternalTracks() method in (https://github.com/kaltura/playkit-js/blob/master/src/track/external-captions-handler.js#L118) since it is relying on the textTracks.langth.

and that bring the method the _markActiveTrack(track: Track) method on https://github.com/kaltura/playkit-js/blob/master/src/player.js#L2414 to mark both tracks as active

fix: in the native adapter not relying on the for index which progresses regardless of actual track index

solves: FEC-11655

src/engines/html5/media-source/adapters/native-adapter.js

@@ -698,6 +698,7 @@ export default class NativeAdapter extends BaseMediaSourceAdapter {
     const captionsTextTrackLanguageCodes = [this._config.captionsTextTrack1LanguageCode, this._config.captionsTextTrack2LanguageCode];
     const textTracks = this._videoElement.textTracks;
     const parsedTracks = [];
+    let internalTrackIndex = 0;
     if (textTracks) {
       for (let i = 0; i < textTracks.length; i++) {
         if (!PKTextTrack.isExternalTrack(textTracks[i])) {
@@ -707,7 +708,7 @@ export default class NativeAdapter extends BaseMediaSourceAdapter {
             label: textTracks[i].label,
             language: textTracks[i].language,
             available: true,
-            index: i
+            index: internalTrackIndex++
           };
           if (settings.kind === PKTextTrack.KIND.SUBTITLES) {
             parsedTracks.push(new PKTextTrack(settings));