Doesn't attack Rogue Wizard?

[10:34:43 PM:339] System.NullReferenceException: Object reference not set to an instance of an object.
at TreeSharp.Decorator.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at TreeSharp.PrioritySelector.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at TreeSharp.Decorator.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at TreeSharp.PrioritySelector.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at TreeSharp.Decorator.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at TreeSharp.PrioritySelector.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at TreeSharp.PrioritySelector.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at TreeSharp.PrioritySelector.#h.#nF.MoveNext()
at (Object )
at TreeSharp.Composite.Tick(Object context)
at Styx.Logic.BehaviorTree.TreeRoot.Tick()

that's what it shows............

EDIT: actually doesn't attack any monster. :/