internal server error

[AGTHARN]

[08:58:37] [Server thread/CRITICAL]: Error: "Call to a member function setBlock() on null" (EXCEPTION) in "plugins/BurgerSpawners_dev-69.phar/src/Heisenburger69/BurgerSpawners/Utilities/Forms" at line 157
[08:58:37] [Server thread/DEBUG]: #0 plugins/BurgerSpawners_dev-69.phar/src/Heisenburger69/BurgerSpawners/libs/jojoe77777/FormAPI/Form(46): Heisenburger69\BurgerSpawners\Utilities\Forms::Heisenburger69\BurgerSpawners\Utilities{closure}(object alvin0319\OffHand\OffHandPlayer, array[2])
[08:58:37] [Server thread/DEBUG]: #1 src/pocketmine/Player(3442): Heisenburger69\BurgerSpawners\libs\jojoe77777\FormAPI\Form->handleResponse(object alvin0319\OffHand\OffHandPlayer, array[2])
[08:58:37] [Server thread/DEBUG]: #2 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(264): pocketmine\Player->onFormSubmit(integer 221, array[2])
[08:58:37] [Server thread/DEBUG]: #3 src/pocketmine/network/mcpe/protocol/ModalFormResponsePacket(49): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleModalFormResponse(object pocketmine\network\mcpe\protocol\ModalFormResponsePacket)
[08:58:37] [Server thread/DEBUG]: #4 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\ModalFormResponsePacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[08:58:37] [Server thread/DEBUG]: #5 src/pocketmine/network/mcpe/protocol/BatchPacket(126): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\ModalFormResponsePacket)
[08:58:37] [Server thread/DEBUG]: #6 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\BatchPacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[08:58:37] [Server thread/DEBUG]: #7 src/pocketmine/Player(3118): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[08:58:37] [Server thread/DEBUG]: #8 src/pocketmine/network/mcpe/RakLibInterface(169): pocketmine\Player->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[08:58:37] [Server thread/DEBUG]: #9 vendor/pocketmine/raklib/src/server/ServerHandler(99): pocketmine\network\mcpe\RakLibInterface->handleEncapsulated(string[19] 70.253.79.135 60886, object raklib\protocol\EncapsulatedPacket, integer 0)
[08:58:37] [Server thread/DEBUG]: #10 src/pocketmine/network/mcpe/RakLibInterface(109): raklib\server\ServerHandler->handlePacket()
[08:58:37] [Server thread/DEBUG]: #11 src/pocketmine/network/mcpe/RakLibInterface(99): pocketmine\network\mcpe\RakLibInterface->process()
[08:58:37] [Server thread/DEBUG]: #12 vendor/pocketmine/snooze/src/SleeperHandler(123): pocketmine\network\mcpe\RakLibInterface->pocketmine\network\mcpe{closure}()
[08:58:37] [Server thread/DEBUG]: #13 vendor/pocketmine/snooze/src/SleeperHandler(85): pocketmine\snooze\SleeperHandler->processNotifications()
[08:58:37] [Server thread/DEBUG]: #14 src/pocketmine/Server(2146): pocketmine\snooze\SleeperHandler->sleepUntil(double 1588496317.1644)
[08:58:37] [Server thread/DEBUG]: #15 src/pocketmine/Server(1990): pocketmine\Server->tickProcessor()
[08:58:37] [Server thread/DEBUG]: #16 src/pocketmine/Server(1584): pocketmine\Server->start()
[08:58:37] [Server thread/DEBUG]: #17 src/pocketmine/PocketMine(273): pocketmine\Server->__construct(object BaseClassLoader, object pocketmine\utils\MainLogger, string[16] /home/container/, string[24] /home/container/plugins/)
[08:58:37] [Server thread/DEBUG]: #18 src/pocketmine/PocketMine(296): pocketmine\server()
[08:58:37] [Server thread/DEBUG]: #19 (11): require(string[71] phar:///home/container/PocketMine-MP.phar/src/pocketmine/PocketMine.php)