fix: Fix error thrown after catching null error (#7177)

Sometimes, this catches a "null" error. This shouldn't happen, but if it
does, we shouldn't throw yet another exception while handling it.

lib/player.js

@@ -1749,7 +1749,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       this.dispatchEvent(shaka.Player.makeEvent_(
           shaka.util.FakeEvent.EventName.Loaded));
     } catch (error) {
-      if (error.code != shaka.util.Error.Code.LOAD_INTERRUPTED) {
+      if (error && error.code != shaka.util.Error.Code.LOAD_INTERRUPTED) {
         await this.unload(/* initializeMediaSource= */ false);
       }
       throw error;