make chunk lightmap optional

src/voxels/Chunk.cpp

@@ -8,7 +8,8 @@
 #include "util/data_io.hpp"
 #include "voxel.hpp"
 
-Chunk::Chunk(int xpos, int zpos) : x(xpos), z(zpos) {
+Chunk::Chunk(int xpos, int zpos, std::shared_ptr<Lightmap> lightmap)
+    : x(xpos), z(zpos), lightmap(std::move(lightmap)) {
     bottom = 0;
     top = CHUNK_H;
 }
@@ -56,15 +57,6 @@ std::shared_ptr<Inventory> Chunk::getBlockInventory(uint x, uint y, uint z)
     return found->second;
 }
 
-std::unique_ptr<Chunk> Chunk::clone() const {
-    auto other = std::make_unique<Chunk>(x, z);
-    for (uint i = 0; i < CHUNK_VOL; i++) {
-        other->voxels[i] = voxels[i];
-    }
-    other->lightmap.set(&lightmap);
-    return other;
-}
-
 /**
   Current chunk format:
     - byte-order: little-endian