Follow-up to f98edf8: better checks for application restart.

- Fixes resource reloading when OsuGroupList is empty (i.e. if user has no beatmaps installed).
- OsuGroupList is no longer initialized with a class instance; OsuGroupList.create() is called by OsuParser.
- Also clear 'lastOsu' field in MusicController.reset().  Fixes theme song not playing on restart if it was the last track played (i.e. if no beatmaps installed).
- Call MusicController.reset() last so that more garbage is collected.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

src/itdelatrisu/opsu/audio/MusicController.java

@@ -83,9 +83,7 @@ public class MusicController {
 	 * Plays an audio file at the preview position.
 	 */
 	public static void play(final OsuFile osu, final boolean loop) {
-		boolean play = (lastOsu == null || !osu.audioFilename.equals(lastOsu.audioFilename));
-		lastOsu = osu;
-		if (play) {
+		if (lastOsu == null || !osu.audioFilename.equals(lastOsu.audioFilename)) {
 			reset();
 			System.gc();
 
@@ -114,6 +112,7 @@ public class MusicController {
 				break;
 			}
 		}
+		lastOsu = osu;
 	}
 
 	/**
@@ -335,6 +334,7 @@ public class MusicController {
 		}
 
 		// reset state
+		lastOsu = null;
 		themePlaying = false;
 		pauseTime = 0f;
 		trackDimmed = false;