Fix possible dupe glitch

Author: dries-c

src/muqsit/invmenu/InvMenuEventHandler.php

@@ -62,20 +62,18 @@ public function onInventoryTransaction(InventoryTransactionEvent $event) : void{
 
 		$player_instance = $this->player_manager->get($player);
 		$current = $player_instance->getCurrent();
-		if($current === null){
-			foreach($transaction->getActions() as $action){
-				if($action instanceof SlotChangeAction && $action->getInventory() instanceof InvMenuInventory){
-				    $event->cancel();
-				    return;
-				}
-			}
-			return;
-		}
-
-		$inventory = $current->menu->getInventory();
+		$inventory = $current?->menu->getInventory();
 		$network_stack_callbacks = [];
 		foreach($transaction->getActions() as $action){
-			if(!($action instanceof SlotChangeAction) || $action->getInventory() !== $inventory){
+			if(!($action instanceof SlotChangeAction)){
+				continue;
+			}
+
+			if($action->getInventory() !== $inventory){
+				if($action->getInventory() instanceof InvMenuInventory){
+					$event->cancel();
+					return;
+				}
 				continue;
 			}