NodeAtX/Y is the coordonates of the Xth point in the path calculated by the pathfinder. I take the last one : the destination. -1 is because arrays in js are 0-based, first element is on index 0. It can never be less than 1, because you always have a destination if the path is found.
Even if I made a mistake, let's say -2, it would return Null, equivalent to 0 I think in this case, the cross would be at 0,0, but the sprite wouldn't move, it wouldn't have any path to follow ^^
You can now see where they are heading. I couldn't correctly debug your code without adding some correct debug. The enemies were going somewhere slowly, it took decades to understand the problem at first ^^