Internal server error on join

[Mohagames205]

• Issue Description: When I join I get "Internal server error"

• Version: 1.5.1

• Server Version: Pocketmine 3.8.3

• Crashdump, backtrace or other files:```[13:21:17] [Server thread/INFO]: Mohagames205[/81.245.220.164:57978] logged in with entity id 5 at (DEEP SUPERFLAT NO STRUCTURES, -701, 31, 893)
  [13:21:23] [Server thread/CRITICAL]: Error: "Call to a member function count() on null" (EXCEPTION) in "plugins/MultiWorld.phar/src/czechpmdevs/multiworld/api/WorldGameRulesAPI" at line 60
  [13:21:23] [Server thread/DEBUG]: #0 plugins/MultiWorld.phar/src/czechpmdevs/multiworld/api/WorldGameRulesAPI(177): czechpmdevs\multiworld\api\WorldGameRulesAPI::getLevelGameRules(pocketmine\level\Level object)
  [13:21:23] [Server thread/DEBUG]: Feature #1 plugins/MultiWorld.phar/src/czechpmdevs/multiworld/EventListener(85): czechpmdevs\multiworld\api\WorldGameRulesAPI::updateGameRules(pocketmine\Player object)
  [13:21:23] [Server thread/DEBUG]: Feature request: add world editor #2 src/pocketmine/plugin/MethodEventExecutor(38): czechpmdevs\multiworld\EventListener->onJoin(pocketmine\event\player\PlayerJoinEvent object)
  [13:21:23] [Server thread/DEBUG]: přidej češtinu #3 src/pocketmine/plugin/RegisteredListener(98): pocketmine\plugin\MethodEventExecutor->execute(czechpmdevs\multiworld\EventListener object, pocketmine\event\player\PlayerJoinEvent object)
  [13:21:23] [Server thread/DEBUG]: tak já dám češtinu do readme :D #4 src/pocketmine/event/Event(99): pocketmine\plugin\RegisteredListener->callEvent(pocketmine\event\player\PlayerJoinEvent object)
  [13:21:23] [Server thread/DEBUG]: "Undefined index: creativeWorlds" #5 src/pocketmine/Player(1082): pocketmine\event\Event->call()
  [13:21:23] [Server thread/DEBUG]: MultiWorld does not support Apollo #6 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(297): pocketmine\Player->doFirstSpawn()
  [13:21:23] [Server thread/DEBUG]: Please update this plugin on poggit,thank you. #7 src/pocketmine/network/mcpe/protocol/SetLocalPlayerAsInitializedPacket(45): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleSetLocalPlayerAsInitialized(pocketmine\network\mcpe\protocol\SetLocalPlayerAsInitializedPacket object)
  [13:21:23] [Server thread/DEBUG]: Update plugin.yml #8 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(109): pocketmine\network\mcpe\protocol\SetLocalPlayerAsInitializedPacket->handle(pocketmine\network\mcpe\PlayerNetworkSessionAdapter object)
  [13:21:23] [Server thread/DEBUG]: Processing of players at the same level when "/mw delete" #9 src/pocketmine/network/mcpe/protocol/BatchPacket(123): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(pocketmine\network\mcpe\protocol\SetLocalPlayerAsInitializedPacket object)
  [13:21:23] [Server thread/DEBUG]: Add Japanese #10 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(109): pocketmine\network\mcpe\protocol\BatchPacket->handle(pocketmine\network\mcpe\PlayerNetworkSessionAdapter object)
  [13:21:23] [Server thread/DEBUG]: Please Update To 3.0.0-ALPHA12 #11 src/pocketmine/Player(3124): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(pocketmine\network\mcpe\protocol\BatchPacket object)
  [13:21:23] [Server thread/DEBUG]: Update README.md #12 src/pocketmine/network/mcpe/RakLibInterface(169): pocketmine\Player->handleDataPacket(pocketmine\network\mcpe\protocol\BatchPacket object)
  [13:21:23] [Server thread/DEBUG]: Plugin needs to be update #13 vendor/pocketmine/raklib/src/server/ServerHandler(99): pocketmine\network\mcpe\RakLibInterface->handleEncapsulated(string 81.245.220.164 57978, raklib\protocol\EncapsulatedPacket object, integer 0)
  [13:21:23] [Server thread/DEBUG]: New PMMP Bug Fixes #14 src/pocketmine/network/mcpe/RakLibInterface(109): raklib\server\ServerHandler->handlePacket()
  [13:21:23] [Server thread/DEBUG]: Error when deleting world #15 src/pocketmine/network/mcpe/RakLibInterface(99): pocketmine\network\mcpe\RakLibInterface->process()
  [13:21:23] [Server thread/DEBUG]: 1.4.3 #16 vendor/pocketmine/snooze/src/SleeperHandler(123): pocketmine\network\mcpe\RakLibInterface->pocketmine\network\mcpe{closure}()
  [13:21:23] [Server thread/DEBUG]: Bump API to 3.0.0 #17 vendor/pocketmine/snooze/src/SleeperHandler(85): pocketmine\snooze\SleeperHandler->processNotifications()
  [13:21:23] [Server thread/DEBUG]: Report a bug #18 src/pocketmine/Server(2339): pocketmine\snooze\SleeperHandler->sleepUntil(double 1559827283.9472)
  [13:21:23] [Server thread/DEBUG]: Fix #18 and another error occur leading to server crash #19 src/pocketmine/Server(2196): pocketmine\Server->tickProcessor()
  [13:21:23] [Server thread/DEBUG]: Add New NetherGenerator? #20 src/pocketmine/Server(1775): pocketmine\Server->start()
  [13:21:23] [Server thread/DEBUG]: Bug on Altay #21 src/pocketmine/PocketMine(266): pocketmine\Server->__construct(BaseClassLoader object, pocketmine\utils\MainLogger object, string /home/container/, string /home/container/plugins/)
  [13:21:23] [Server thread/DEBUG]: Delete EnderGenerator to fix #21 #22 (1): require(string phar:///home/container/PocketMine-MP.phar/src/pocketmine/PocketMine.php)
  [13:21:23] [Server thread/INFO]: [StaffChat] Mohagames205 disconnected
  [13:21:23] [Server thread/INFO]: Mohagames205 left the game
  [13:21:23] [Server thread/INFO]: Mohagames205[/81.245.220.164:57978] logged out due to Internal server error
  [13:21:23] [RakLibServer thread/NOTICE]: Blocked 81.245.220.164 for 5 seconds

[GamakCZ]

thx for report

[GamakCZ]

It should be fixed in next release