Disables play/pause button when there's nothing to play

PiperOrigin-RevId: 502571320

libraries/ui/src/main/java/androidx/media3/ui/PlayerControlView.java

@@ -980,6 +980,9 @@ public class PlayerControlView extends FrameLayout {
       ((ImageView) playPauseButton)
           .setImageDrawable(getDrawable(getContext(), resources, drawableRes));
       playPauseButton.setContentDescription(resources.getString(stringRes));
+
+      boolean enablePlayPause = shouldEnablePlayPauseButton();
+      updateButton(enablePlayPause, playPauseButton);
     }
   }
 
@@ -1497,6 +1500,10 @@ public class PlayerControlView extends FrameLayout {
     }
   }
 
+  private boolean shouldEnablePlayPauseButton() {
+    return player != null && !player.getCurrentTimeline().isEmpty();
+  }
+
   private boolean shouldShowPauseButton() {
     return player != null
         && player.getPlaybackState() != Player.STATE_ENDED