Crash no name world

**Steps to reproduce the error:**

1.- /spleef

2.- [New arena]

3.- [New world]

4.- (Do not write anything in the world)

5.- [Send]

**Crash:**

[14:38:27] [Server thread/CRITICAL]: pocketmine\level\LevelException: "Invalid empty world name" (EXCEPTION) in "src/pocketmine/Server" at line 937
[14:38:27] [Server thread/DEBUG]: #0 plugins/Spleef_dev-3.phar/src/xenialdan/Spleef/Loader(163): pocketmine\Server->loadLevel(string[0] )
[14:38:27] [Server thread/DEBUG]: #1 plugins/Spleef_dev-3.phar/src/xenialdan/Spleef/libs/xenialdan/customui/windows/CustomForm(103): xenialdan\Spleef\Loader->xenialdan\Spleef\{closure}(object pocketmine\Player, array[2])
[14:38:27] [Server thread/DEBUG]: #2 src/pocketmine/Player(3588): xenialdan\Spleef\libs\xenialdan\customui\windows\CustomForm->handleResponse(object pocketmine\Player, array[2])
[14:38:27] [Server thread/DEBUG]: #3 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(264): pocketmine\Player->onFormSubmit(integer 3, array[2])
[14:38:27] [Server thread/DEBUG]: #4 src/pocketmine/network/mcpe/protocol/ModalFormResponsePacket(49): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleModalFormResponse(object pocketmine\network\mcpe\protocol\ModalFormResponsePacket)
[14:38:27] [Server thread/DEBUG]: #5 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\ModalFormResponsePacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[14:38:27] [Server thread/DEBUG]: #6 src/pocketmine/network/mcpe/protocol/BatchPacket(127): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\ModalFormResponsePacket)
[14:38:27] [Server thread/DEBUG]: #7 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\BatchPacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[14:38:27] [Server thread/DEBUG]: #8 src/pocketmine/Player(3235): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[14:38:27] [Server thread/DEBUG]: #9 src/pocketmine/network/mcpe/RakLibInterface(169): pocketmine\Player->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[14:38:27] [Server thread/DEBUG]: #10 vendor/pocketmine/raklib/src/server/ServerHandler(99): pocketmine\network\mcpe\RakLibInterface->handleEncapsulated(string[17] 81.0.33.209 33252, object raklib\protocol\EncapsulatedPacket, integer 0)
[14:38:27] [Server thread/DEBUG]: #11 src/pocketmine/network/mcpe/RakLibInterface(109): raklib\server\ServerHandler->handlePacket()
[14:38:27] [Server thread/DEBUG]: #12 src/pocketmine/network/mcpe/RakLibInterface(99): pocketmine\network\mcpe\RakLibInterface->process()
[14:38:27] [Server thread/DEBUG]: #13 vendor/pocketmine/snooze/src/SleeperHandler(123): pocketmine\network\mcpe\RakLibInterface->pocketmine\network\mcpe\{closure}()
[14:38:27] [Server thread/DEBUG]: #14 vendor/pocketmine/snooze/src/SleeperHandler(85): pocketmine\snooze\SleeperHandler->processNotifications()
[14:38:27] [Server thread/DEBUG]: #15 src/pocketmine/Server(2157): pocketmine\snooze\SleeperHandler->sleepUntil(double 1593866307.3244)
[14:38:27] [Server thread/DEBUG]: #16 src/pocketmine/Server(1994): pocketmine\Server->tickProcessor()
[14:38:27] [Server thread/DEBUG]: #17 src/pocketmine/Server(1588): pocketmine\Server->start()
[14:38:27] [Server thread/DEBUG]: #18 src/pocketmine/PocketMine(273): pocketmine\Server->__construct(object BaseClassLoader, object pocketmine\utils\MainLogger, string[16] /home/container/, string[24] /home/container/plugins/)
[14:38:27] [Server thread/DEBUG]: #19 src/pocketmine/PocketMine(304): pocketmine\server()
[14:38:27] [Server thread/DEBUG]: #20 (11): require(string[71] phar:///home/container/PocketMine-MP.phar/src/pocketmine/PocketMine.php)

Start in src/xenialdan/Spleef/Loader.php around line 163, where the custom form response calls PocketMine's loadLevel with the submitted world name. Reproduce the New arena → New world flow while leaving the name empty. Done means submitting an empty name no longer causes the Invalid empty world name crash.

Written by the indexing model from the issue text.