Race condition error while switching audio tracks

[diogoazevedos]

What version of Shaka Player are you using?
4.4.1

Are you using the demo app or your own custom app?
Custom

If custom app, can you reproduce the issue using our demo app?
Yes

What browser and OS are you using?
Chrome macOS

What are the manifest and license server URIs?
https://player-static-server-assets.mediafe-prd.s.joyn.de/media/vod/multi-audio/dash/manifest.mpd

What did you do?

• Go to https://shaka-player-demo.appspot.com/demo/
• Execute the following:

shakaDemoMain.video_.addEventListener('durationchange', () => shakaDemoMain.player_.selectAudioLanguage('de', 'alternate'))
shakaDemoMain.player_.load('https://player-static-server-assets.mediafe-prd.s.joyn.de/media/vod/multi-audio/dash/manifest.mpd');

The error seems to be caused by a race condition when .release() is called before .createUrisCb():

shaka-player/lib/dash/segment_template.js

Lines 679 to 684 in d4dca2a

	release() {
	super.release();
	this.templateInfo_ = null;
	// We cannot release other fields, as segment index can
	// be recreated using only template info.
	}

shaka-player/lib/dash/segment_template.js

Lines 870 to 880 in d4dca2a

	const createUrisCb = () => {
	return shaka.dash.TimelineSegmentIndex
	.createUris_(
	this.templateInfo_.mediaTemplate,
	this.representationId_,
	segmentReplacement,
	this.bandwidth_,
	timeReplacement,
	this.baseUris_,
	);
	};

The issue was introduced via #5061

What did you expect to happen?
The audio track is selected and no error is thrown.

What actually happened?
The audio track is selected and the player throws the error:

TypeError: Cannot read properties of null (reading 'mediaTemplate')
    at shaka.media.SegmentReference.createUrisCb [as getUrisInner] (segment_template.js:873:36)
    at shaka.media.SegmentReference.getUris (segment_reference.js:291:17)
    at shaka.media.StreamingEngine.dispatchFetch_ (streaming_engine.js:2226:19)
    at shaka.media.StreamingEngine.fetch_ (streaming_engine.js:2195:17)
    at shaka.media.StreamingEngine.fetchAndAppend_ (streaming_engine.js:1411:35)