Store map path in MapPreview.

OpenRA.Game/ModData.cs

@@ -166,7 +166,7 @@ namespace OpenRA
 				throw new InvalidDataException("Invalid map uid: {0}".F(uid));
 
 			// Operate on a copy of the map to avoid gameplay state leaking into the cache
-			var map = new Map(MapCache[uid].Map.Path);
+			var map = new Map(MapCache[uid].Path);
 
 			LoadTranslations(map);