Fix memory leak when switching providers within a playlist [Delivers #79305128 #79031288]

[Fixes #79305128 #79031288]
Also i think this is wrong, im not sure but looks like if defaultProvider is set, this is going to always override the new provider, for example if the defaultProvider dont support youtube, and the item is a youtube video, html5.chooseProvider returns the provider for youtube, but because defaultProvider is is set the youtube provider is not used..

Fix:
 _currentProvider = new Provider(_model.id) || defaultProvider;