[backwards] Have Backwards fallback to Mirror.

Not all gametypes require Backwards: they will fall
through to Mirror. Otherwise, catch it here.

src/NoteDataUtil.cpp

@@ -1208,8 +1208,9 @@ static void GetTrackMapping( StepsType st, NoteDataUtil::TrackMapping tt, int Nu
 		}
 
 		break;
-	case NoteDataUtil::mirror:
+	case NoteDataUtil::backwards:
 	{
+		// If a Pump game type, treat differently. Otherwise, send to mirror.
 		switch (st)
 		{
 			case StepsType_pump_single:
@@ -1252,15 +1253,15 @@ static void GetTrackMapping( StepsType st, NoteDataUtil::TrackMapping tt, int Nu
 				iTakeFromTrack[5] = 0;
 				break;
 			}
-				default:
+			default:;
+		}
+	}
+	case NoteDataUtil::mirror:
 		{
 			for( int t=0; t<NumTracks; t++ )
 				iTakeFromTrack[t] = NumTracks-t-1;
 			break;
 		}
-			}
-			break;
-		}
 	case NoteDataUtil::shuffle:
 	case NoteDataUtil::super_shuffle:		// use shuffle code to mix up HoldNotes without creating impossible patterns
 		{