Reset StitchedSprites when the atlas is stitched

- Might fix simi's slime issue

src/main/java/com/jozufozu/flywheel/core/AtlasStitcher.java

@@ -33,6 +33,7 @@ public class AtlasStitcher {
 				.equals(PlayerContainer.BLOCK_ATLAS_TEXTURE))
 			return;
 
+		sprites.forEach(StitchedSprite::reset);
 		sprites.stream()
 				.map(StitchedSprite::getLoc)
 				.forEach(event::addSprite);

src/main/java/com/jozufozu/flywheel/core/StitchedSprite.java

@@ -11,7 +11,7 @@ public class StitchedSprite {
 
 	TextureAtlasSprite sprite;
 
-	public StitchedSprite(ResourceLocation loc) {
+	StitchedSprite(ResourceLocation loc) {
 		this.loc = loc;
 	}
 
@@ -28,4 +28,8 @@ public class StitchedSprite {
 
 		return sprite;
 	}
+
+	void reset() {
+		sprite = null;
+	}
 }