Steps to reproduce
1. Create a new project.
2. Create a material using a Mobile Bumped Specular 1 Directional Light shader.
3. Create a 3D primitive, or alternatively import a 3D object, and set it to Static
4. Apply the newly created material to it.
5. Add a Directional Light to a scene (if not already present) and set its light mode to Baked.
6. Bake the lighting using either the Progressive Lightmapper or Enlighten.
7. Notice how the object turned completely black.

Expected behavior
Objects using the Mobile Bumped Specular 1 Directional Light shader should receive proper baked lighting information.

Actual behavior
Objects using the Mobile Bumped Specular 1 Directional Light shader turn completely black.

Notes
The results were tested and reproduced in Unity Version 5.6.5p1 (b5fcd78dd1ab).