Search: Fix null object dereference.

Spotted while going through application logs. It seems
searchView.headerItem can be null in some cases.
VideoPlayer: Implement support for selecting video quality.

Depending on the video 360p, 720p or 1080p qualities can be selected.
Remove UtilityWorkerScript.

Only one use case of the object remained and it was not critical anyway
so remove it to reduce application complexity.