When using a custom shader and the Enum Property with fraction numbers, the resulting drop-down menu in material inspector does not allow for those fractioned number options to be selected.

Steps to reproduce:
1. Open attached project
2. Open material in inspector
3. Drag over the shader on the material in inspector
4. Observe the 2 drop-down menus
5. Try to select OptionB or OptionC in the first dropdown menu that says "This uses fractions"
6. Those numbers are not selected (OptionB and OptionC are fraction numbers defined in the shader)

Expected outcome: Since this is a float variable, the values get selected normally
Actual outcome: The drop-down displays the available options, but fails to select them when they are clicked

Reproduced on: 5.4.0f3, 5.5.0p2, 5.5.2p4, 5.5.3f1, 5.6.0f3, 2017.1.0a6