1. Select the null’s position keyframes and copy them (Cmd or ctrl +C).
2. Make a new solid layer and make a mask consisting of a single vertex with the pen tool
3. Reveal the Mask and select the Mask Path then paste, this should create a mask with the same path as the null’s position.
4. Select the Mask Path and copy (Cmd or ctrl +C).
5. Open a new Illustrator document and paste.

