Checking blackboard value doesn't work?

Hi! I’m currently working with a behavior tree for my characters and I’ve stumbled upon yet another problem.

As the image below shows I have a decorator that will check if an actor is not null. Then use this to determine whether the character will start attacking its enemy or not. The problem is that even if the blackboard value is set, the behavior tree fires the node that checks if the reverse is true anyway.

What am I doing wrong?