fix: fix support clear and encrypted periods (#4606)

Closes #4512

lib/media/drm_engine.js

@@ -407,6 +407,7 @@ shaka.media.DrmEngine = class {
     if (this.mediaKeysAttached_) {
       await this.mediaKeysAttached_;
 
+      this.destroyer_.ensureNotDestroyed();
       return;
     }
 
@@ -484,14 +485,12 @@ shaka.media.DrmEngine = class {
 
     /**
      * We can attach media keys before the playback actually begins when:
-     *  - Using legacy implementations requires MediaKeys to be set before
-     *    having webkitneedkey / msneedkey event, which will be translated as
-     *    an encrypted event by the polyfills
+     *  - If we are not using FairPlay Modern EME
      *  - Some initData already has been generated (through the manifest)
      *  - In case of an offline session
      */
     if (manifestInitData ||
-        shaka.util.Platform.isMediaKeysPolyfilled() ||
+        this.currentDrmInfo_.keySystem !== 'com.apple.fps' ||
         this.offlineSessionIds_.length) {
       await this.attachMediaKeys_();
     }