fix dumb bug in map importer

OpenRA.FileFormats/Filesystem/Folder.cs

@@ -63,7 +63,10 @@ namespace OpenRA.FileFormats
 		}
 		
 		public void Write(Dictionary<string, byte[]> contents)
-		{
+		{
+			if (!Directory.Exists(path))
+				Directory.CreateDirectory(path);
+
 			foreach (var file in contents)
 				using (var dataStream = File.Create(Path.Combine(path, file.Key)))
 					using (var writer = new BinaryWriter(dataStream))