Void generator default block

[dadodasyra]

Describe the bug The server crash while trying to save the only block in void world.

To Reproduce Steps to reproduce the behavior:

1. Generate a void world
2. Leave the default block at the spawn (which is in fact shown as a info_update block)
3. /save-all the server or wait auto save
4. Server will crash

Expected behavior The default should be stone, grass, or idk what.

Screenshots

[20:42:45.694] [Server thread/CRITICAL]: pocketmine\data\bedrock\block\BlockStateSerializeException: "No serializer registered for pocketmine\block\UnknownBlock with type ID 40" (EXCEPTION) in "pmsrc/src/data/bedrock/block/convert/BlockObjectToStateSerializer" at line 253
--- Stack trace ---
  #0 pmsrc/src/data/bedrock/block/convert/BlockObjectToStateSerializer(211): pocketmine\data\bedrock\block\convert\BlockObjectToStateSerializer->serializeBlock(object pocketmine\block\UnknownBlock#88109)
  #1 pmsrc/src/world/format/io/leveldb/LevelDB(228): pocketmine\data\bedrock\block\convert\BlockObjectToStateSerializer->serialize(int 10282)
  #2 pmsrc/src/world/format/io/leveldb/LevelDB(761): pocketmine\world\format\io\leveldb\LevelDB->serializeBlockPalette(object pocketmine\utils\BinaryStream#174979, object pocketmine\world\format\PalettedBlockArray#86960)
  #3 pmsrc/src/world/World(2931): pocketmine\world\format\io\leveldb\LevelDB->saveChunk(int 16, int 16, object pocketmine\world\format\io\ChunkData#143538, int -1)
  #4 pmsrc/src/world/World(633): pocketmine\world\World->unloadChunk(int 16, int 16, false)
  #5 pmsrc/src/world/WorldManager(163): pocketmine\world\World->onUnload()
  #6 pmsrc/src/Server(1467): pocketmine\world\WorldManager->unloadWorld(object pocketmine\world\World#181786, true)
  #7 pmsrc/src/Server(1065): pocketmine\Server->forceShutdown()
  #8 pmsrc/src/PocketMine(334): pocketmine\Server->__construct(object pocketmine\thread\ThreadSafeClassLoader#3, object pocketmine\utils\MainLogger#6, string[29] /root/servers/miscs/betatest/, string[37] /root/servers/miscs/betatest/plugins/)
  #9 pmsrc/src/PocketMine(357): pocketmine\server()
  #10 pmsrc(11): require(string[73] phar:///root/servers/miscs/betatest/PocketMine-MP.phar/src/PocketMine.php)
--- End of exception information ---
[20:42:45.694] [Server thread/EMERGENCY]: Crashed while crashing, killing process```

**System information (please complete the following information):**
- OS: Debian 11
- PHP Version: 8.3
- MultiWorld Version: 2.1.1

**Additional context**
Add any other context about the problem here.