optimize Chunks::save

src/voxels/Chunks.cpp

@@ -743,13 +743,16 @@ void Chunks::save(Chunk* chunk) {
             )
         );
         auto entities = level->entities->getAllInside(aabb);
-        auto root = dynamic::create_map();
+        dynamic::Map_sptr root = nullptr;
         if (!entities.empty()) {
+            root = dynamic::create_map();
             root->put("data", level->entities->serialize(entities));
             level->entities->despawn(std::move(entities));
             chunk->flags.entities = true;
         }
-        worldFiles->getRegions().put(chunk, json::to_binary(root, true));
+        worldFiles->getRegions().put(
+            chunk, root ? json::to_binary(root, true) : std::vector<ubyte>()
+        );
     }
 }