These are dummy files. You can ignore them. But that's a behaviour added after 2.0.4 and before 2.0.8 somewhen, so either in 2.0.5 or 2.0.6 or 2.0.7. No clue if it's intentional.
Edit: Seems to be intentional.
Write out empty add-on data XML files if a data type contains no entries.
These are dummy files. You can ignore them. But that's a behaviour added after 2.0.4 and before 2.0.8 somewhen, so either in 2.0.5 or 2.0.6 or 2.0.7. No clue if it's intentional.