message: Check if the destination chunk exists after leaving the source chunk
  This fixes a crash if a player does a /refresh in the zeroeth chunk.
diff: @@ -161,12 +161,13 @@ static void emptyChunk(ChunkPos chunkPos) {
  void Chunking::updateEntityChunk(const EntityRef& ref, ChunkPos from, ChunkPos to) {
  Entity* ent = ref.getEntity();
  + // move to other chunk's player set
  + untrackEntity(from, ref); // this will delete the chunk if it's empty
  +
  // if the new chunk doesn't exist, make it first
  if (!chunkExists(to))
  newChunk(to);
  - // move to other chunk's player set
  - untrackEntity(from, ref); // this will delete the chunk if it's empty
  trackEntity(to, ref);
  // calculate viewable chunks from both points
  