If you're using Create Nulls from Path, the Contents of the Shape Layer needs to be a Path (not a Rectangle, an Ellipse nor a Polystar) and the "Path" parameter needs to be selected when you click "Nulls Follow Points".

- Choose Window > Create Nulls From Path.
- Select the Path parameter.
- Click Nulls Follow Points.
You should be good to parent your brick artwork to which ever resulting Null layer is at the end point of the path. You can delete any unused Null Layers.
The path can be open or closed.
If you happen to need a rectangle, ellipse or polystar, you can draw one in Illustrator and copy and paste that to the selected Path parameter.
-Warren