System Information
Archlinux
Nvidia 7900GT

Blender Version
Broken:

2.69 Release (from blender.org)
2.69.7 Build hash: b2fdc59 Date: 2013-12-20 00:40 (From the buildbot)

Short description of error
Adding a new vertex group without assigning anything and using it in the mask modifier does not give expected results.

Exact steps for others to reproduce the error

1. Open a new file
2. Add a new vertex group without assigning anything to it
3. Add a mask modifier and select the vertex group. This should hide all the geometry, but it does not.
4. Assign and remove something to the vertex group. The mask modifier now works as expected.

See