AI Blueprint Error

I have been following this tutorial to build my basic AI system https://docs.unrealengine.com/en-us/Engine/AI/BehaviorTrees/QuickStart

I’m now getting an error PIE: Error: Blueprint Runtime Error: Accessed None trying to read property CallFunc_BreakHitResult_HitActor1 from function: ‘ExecuteUbergraph_AgroCheck’ from node: Set Blackboard Value as Vector in graph: EventGraph in object: AgroCheck with description: Accessed None trying to read property CallFunc_BreakHitResult_HitActor1

Can anyone shed some light on what might be causing this? Thanks.

Your hit actor is None/Null. Meaning there is no value. You can check if a value is valid by using the ISValid? node. If valid execute. It will get rid of the error, but why the value is None is another issue.