Accessed None from The BlackBoardValueAsActor to the return node.
Used : https://docs.unrealengine.com/latest/INT/Engine/AI/BehaviorTrees/QuickStart/13/index.html
Video : - YouTube
I´m having the exactly same problem! Hope someone can help us 
Hello everyone,
Could you provide a screenshot of your Decorator blueprint? I’d especially like to see the details panel when you have the Target To Follow variable selected.
Thank you
Hi
In my case, it is a Task:
The Task in the Behavior Tree makes my AI moves to the “MemoryMarker”. the memory marker is the last position of the player when the AI saw him.
So, after reach the position it finishes the Task.
Sometimes, for no reason, it gives this error: Accessed None CallFunc_GetBlackboardValueAsActor
In your Behavior Tree, if you click on the Task, have you set the Blackboard Key in the details panel, as shown in my screenshot below? This will ensure that it is attached to a key that exists in your Blackboard.
In the first task that you posted a screenshot of, is your EventReceiveMoveCompleted ever firing? Would you mind disconnecting that and adding the Finish Execute after the Move To instead?
Are both of these tasks running in the same Behavior Tree as well?
Hi, yes, it is set correctly and the error doesn´t happens all the time, just “sometimes”
very weird
This another Task kills the “MemoryMarker” AFTER the AI gets there, and it doesn´t give me any errors:
From the comments above I’m guessing your memory marker gets (sometimes) garbage-collected before use. How do you create it and how do you keep reference to it to shield it from being GCed? Adding UObjects to a blackboard won’t cut it since BB is storing objects as weak object pointers, which do not count as references for garbage collection purposes.
Cheers,
–mieszko
My god… such a simple thing…
Sorry for bothering you guys, you are tottaly right, thanks so much!!