fix msvc build

src/frontend/ContentGfxCache.hpp

@@ -11,7 +11,7 @@
 class Content;
 class Assets;
 class Atlas;
-struct Block;
+class Block;
 struct UVRegion;
 struct GraphicsSettings;
 

src/graphics/render/Decorator.hpp

@@ -14,7 +14,7 @@ class Chunks;
 class Camera;
 class Assets;
 class Player;
-struct Block;
+class Block;
 class Engine;
 class LevelController;
 class WorldRenderer;

src/graphics/render/ModelsGenerator.hpp

@@ -7,7 +7,7 @@
 struct ItemDef;
 class Assets;
 class Content;
-struct Block;
+class Block;
 
 class ModelsGenerator {
 public: