fixed that old chnks do not disapear

FactoryCraft/Dimension.cpp

@@ -65,6 +65,7 @@ void Dimension::setChunk( Chunk* chunk, Punkt center, World* zWorld )
     cs.lock();
     if( old )
     {
+        zWorld->setVisibility( old, 0 );
         int index = 0;
         for( auto iterator = chunkList.begin(); iterator; ++iterator, ++index )
         {