Listen to media detached

Clears the encrypted event listener from the HTMLMediaElement in controller, and releases the stored reference.

src/controller/eme-controller.ts

@@ -103,6 +103,7 @@ class EMEController extends EventHandler {
   constructor (hls) {
     super(hls,
       Event.MEDIA_ATTACHED,
+      Event.MEDIA_DETACHED,
       Event.MANIFEST_PARSED
     );