Undefined index: skip" (EXCEPTION) in "plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/TradeUI" at line 368

[teracube]

https://poggit.pmmp.io/r/52216/TradeUI_dev-1.phar
https://jenkins.pmmp.io/job/PocketMine-MP/1746/artifact/PocketMine-MP.phar

2019-02-17 [21:35:46] [Server thread/CRITICAL]: ErrorException: "Undefined index: skip" (EXCEPTION) in "plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/TradeUI" at line 368
2019-02-17 [21:35:46] [Server thread/DEBUG]: #0 plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/TradeUI(368): pocketmine\utils\Utils::errorExceptionHandler(integer 8, string Undefined index: skip, string phar:///home/teracube/plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/TradeUI.php, integer 368, array Array())
2019-02-17 [21:35:46] [Server thread/DEBUG]: #1 plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/FormHandler/FormList/GlobalShopForm(15): InfinityGamers\TradeUI\TradeUI->fetchItems(pocketmine\Player object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #2 plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/FormHandler/FormList/GlobalShopForm(64): InfinityGamers\TradeUI\FormHandler\FormList\GlobalShopForm->send(pocketmine\Player object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #3 plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/FormHandler/FormRequest(31): InfinityGamers\TradeUI\FormHandler\FormList\GlobalShopForm->handle(pocketmine\Player object, integer 0)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #4 plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/FormManager(100): InfinityGamers\TradeUI\FormHandler\FormRequest->process(integer 0)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #5 plugins/TradeUI_dev-1.phar/src/InfinityGamers/TradeUI/EventListener(32): InfinityGamers\TradeUI\FormManager->handleForm(pocketmine\Player object, integer 0)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #6 src/pocketmine/plugin/MethodEventExecutor(38): InfinityGamers\TradeUI\EventListener->onDataPacketReceiveEvent(pocketmine\event\server\DataPacketReceiveEvent object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #7 src/pocketmine/plugin/RegisteredListener(98): pocketmine\plugin\MethodEventExecutor->execute(InfinityGamers\TradeUI\EventListener object, pocketmine\event\server\DataPacketReceiveEvent object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #8 src/pocketmine/event/Event(99): pocketmine\plugin\RegisteredListener->callEvent(pocketmine\event\server\DataPacketReceiveEvent object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #9 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(107): pocketmine\event\Event->call()
2019-02-17 [21:35:46] [Server thread/DEBUG]: #10 src/pocketmine/network/mcpe/protocol/BatchPacket(119): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(pocketmine\network\mcpe\protocol\ModalFormResponsePacket object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #11 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(108): pocketmine\network\mcpe\protocol\BatchPacket->handle(pocketmine\network\mcpe\PlayerNetworkSessionAdapter object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #12 src/pocketmine/Player(3111): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(pocketmine\network\mcpe\protocol\BatchPacket object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #13 src/pocketmine/network/mcpe/RakLibInterface(170): pocketmine\Player->handleDataPacket(pocketmine\network\mcpe\protocol\BatchPacket object)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #14 vendor/pocketmine/raklib/src/server/ServerHandler(99): pocketmine\network\mcpe\RakLibInterface->handleEncapsulated(string 81.XXX.XX.36 54117, raklib\protocol\EncapsulatedPacket object, integer 0)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #15 src/pocketmine/network/mcpe/RakLibInterface(110): raklib\server\ServerHandler->handlePacket()
2019-02-17 [21:35:46] [Server thread/DEBUG]: #16 src/pocketmine/network/mcpe/RakLibInterface(100): pocketmine\network\mcpe\RakLibInterface->process()
2019-02-17 [21:35:46] [Server thread/DEBUG]: #17 vendor/pocketmine/snooze/src/SleeperHandler(123): pocketmine\network\mcpe\RakLibInterface->pocketmine\network\mcpe\{closure}()
2019-02-17 [21:35:46] [Server thread/DEBUG]: #18 vendor/pocketmine/snooze/src/SleeperHandler(85): pocketmine\snooze\SleeperHandler->processNotifications()
2019-02-17 [21:35:46] [Server thread/DEBUG]: #19 src/pocketmine/Server(2345): pocketmine\snooze\SleeperHandler->sleepUntil(double 1550435747.0211)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #20 src/pocketmine/Server(2205): pocketmine\Server->tickProcessor()
2019-02-17 [21:35:46] [Server thread/DEBUG]: #21 src/pocketmine/Server(1784): pocketmine\Server->start()
2019-02-17 [21:35:46] [Server thread/DEBUG]: #22 src/pocketmine/PocketMine(250): pocketmine\Server->__construct(BaseClassLoader object, pocketmine\utils\MainLogger object, string /home/teracube/, string /home/teracube/plugins/)
2019-02-17 [21:35:46] [Server thread/DEBUG]: #23 (1): require(string phar:///home/teracube/PocketMine-MP.phar/src/pocketmine/PocketMine.php)
2019-02-17 [21:35:46] [Server thread/INFO]: tetra82 [-]
2019-02-17 [21:35:46] [Server thread/INFO]: tetra82[/81.XXX.XX.36:54117] logged out due to Internal server error
2019-02-17 [21:35:46] [RakLibServer thread/NOTICE]: Blocked 81.XXX.XX.36 for 5 seconds

[xBeastMode]

Steps to reproduce??