[Bug] Invalid Player Causes Error

[UnEnanoMas]

Playername>§g /fly off
[21:07:15] [Server thread/CRITICAL]: Error: "Call to a member function getName() on null" (EXCEPTION) in "plugins/FlyPE_dev-57.phar/src/AGTHARN/FlyPE/Main" at line 239
[21:07:15] [Server thread/CRITICAL]: #0 src/pocketmine/command/PluginCommand(54): AGTHARN\FlyPE\Main->onCommand(object pocketmine\Player, object pocketmine\command\PluginCommand, string[3] fly, array[1])
[21:07:15] [Server thread/CRITICAL]: #1 src/pocketmine/command/SimpleCommandMap(248): pocketmine\command\PluginCommand->execute(object pocketmine\Player, string[3] fly, array[1])
[21:07:15] [Server thread/CRITICAL]: #2 src/pocketmine/Server(1811): pocketmine\command\SimpleCommandMap->dispatch(object pocketmine\Player, string[7] fly off)
[21:07:15] [Server thread/CRITICAL]: #3 src/pocketmine/Player(2311): pocketmine\Server->dispatchCommand(object pocketmine\Player, string[7] fly off)
[21:07:15] [Server thread/CRITICAL]: #4 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(244): pocketmine\Player->chat(string[8] /fly off)
[21:07:15] [Server thread/CRITICAL]: #5 src/pocketmine/network/mcpe/protocol/CommandRequestPacket(54): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleCommandRequest(object pocketmine\network\mcpe\protocol\CommandRequestPacket)
[21:07:15] [Server thread/CRITICAL]: #6 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\CommandRequestPacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[21:07:15] [Server thread/CRITICAL]: #7 src/pocketmine/network/mcpe/protocol/BatchPacket(127): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\CommandRequestPacket)
[21:07:15] [Server thread/CRITICAL]: #8 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\BatchPacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[21:07:15] [Server thread/CRITICAL]: #9 src/pocketmine/Player(3250): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[21:07:15] [Server thread/CRITICAL]: #10 src/pocketmine/network/mcpe/RakLibInterface(169): pocketmine\Player->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[21:07:15] [Server thread/CRITICAL]: #11 vendor/pocketmine/raklib/src/server/ServerHandler(99): pocketmine\network\mcpe\RakLibInterface->handleEncapsulated(string[17] 81.0.36.151 29138, object raklib\protocol\EncapsulatedPacket, integer 0)
[21:07:15] [Server thread/CRITICAL]: #12 src/pocketmine/network/mcpe/RakLibInterface(109): raklib\server\ServerHandler->handlePacket()
[21:07:15] [Server thread/CRITICAL]: #13 src/pocketmine/network/mcpe/RakLibInterface(99): pocketmine\network\mcpe\RakLibInterface->process()
[21:07:15] [Server thread/CRITICAL]: #14 vendor/pocketmine/snooze/src/SleeperHandler(123): pocketmine\network\mcpe\RakLibInterface->pocketmine\network\mcpe{closure}()
[21:07:15] [Server thread/CRITICAL]: #15 vendor/pocketmine/snooze/src/SleeperHandler(85): pocketmine\snooze\SleeperHandler->processNotifications()
[21:07:15] [Server thread/CRITICAL]: #16 src/pocketmine/Server(2157): pocketmine\snooze\SleeperHandler->sleepUntil(double 1598296035.3948)
[21:07:15] [Server thread/CRITICAL]: #17 src/pocketmine/Server(1994): pocketmine\Server->tickProcessor()
[21:07:15] [Server thread/CRITICAL]: #18 src/pocketmine/Server(1588): pocketmine\Server->start()
[21:07:15] [Server thread/CRITICAL]: #19 src/pocketmine/PocketMine(273): pocketmine\Server->__construct(object BaseClassLoader, object pocketmine\utils\MainLogger, string[16] /home/container/, string[24] /home/container/plugins/)
[21:07:15] [Server thread/CRITICAL]: #20 src/pocketmine/PocketMine(304): pocketmine\server()
[21:07:15] [Server thread/CRITICAL]: #21 (11): require(string[71] phar:///home/container/PocketMine-MP.phar/src/pocketmine/PocketMine.php)