PlatformPlayer: Do not close the custom soundfont's synth.

This one is shared by all midi players, so closing it at any point
means that any subsequent midi will play using the default synthesizer

src/org/recompile/mobile/PlatformPlayer.java

@@ -454,7 +454,12 @@ public void deallocate() { } // Prefetch does "nothing" in each internal player
 		public void close() 
 		{
 			midi.close();
-			synthesizer.close();
+			/* 
+			 * We can't close the custom synth, otherwise any new midi files will use the
+			 * default soundfont.
+			 */
+			if (!Manager.useCustomMidi && !Manager.hasLoadedCustomMidi) { synthesizer.close(); }
+
 			midiSequence = null;
 			receiver = null;
 		}