music: check game state before applying sliders on startup

This accesses vars, which typically cannot be accessed when not logged in, or in early startup

runelite-client/src/main/java/net/runelite/client/plugins/music/MusicPlugin.java

@@ -186,7 +186,7 @@ public class MusicPlugin extends Plugin
 			channels = new Channel[]{musicChannel, effectChannel, areaChannel};
 
 			addMusicButtons();
-			if (musicConfig.granularSliders())
+			if (client.getGameState() == GameState.LOGGED_IN && musicConfig.granularSliders())
 			{
 				updateMusicOptions();
 				resetSettingsWindow();