Parameter #3 $icon of static method pocketmine\inventory\data\CreativeGroup::named() expects pocketmine\item\Item, pocketmine\item\Item|null given.

Class pocketmine\inventory\data\CreativeGroup has an uninitialized readonly property $categoryId. Assign it in the constructor.

Class pocketmine\inventory\data\CreativeGroup has an uninitialized readonly property $name. Assign it in the constructor.

Class pocketmine\inventory\data\CreativeGroup has an uninitialized readonly property $icon. Assign it in the constructor.

Readonly property pocketmine\inventory\data\CreativeGroup::$categoryId is assigned outside of the constructor.

Readonly property pocketmine\inventory\data\CreativeGroup::$name is assigned outside of the constructor.

Readonly property pocketmine\inventory\data\CreativeGroup::$icon is assigned outside of the constructor.

Readonly property pocketmine\inventory\data\CreativeGroup::$categoryId is assigned outside of the constructor.

Readonly property pocketmine\inventory\data\CreativeGroup::$name is assigned outside of the constructor.

Readonly property pocketmine\inventory\data\CreativeGroup::$icon is assigned outside of the constructor.