"Fn" Key on Mac can no longer be assigned as a key under "Controls

Put the summary of the bug you're having here

What I expected to happen was:
In previous version the "Fn" key could be assigned as a key under "Controls" and this was convenient as it made sprinting comfortable on mac keyboards.

 

What actually happened was.

Now when you try to add the "Fn" key as a control in "Controls" nothing happens. It acts as if you aren't pressing it.
Steps to Reproduce:
1.Go to "Controls"

2.Select any key to change

3.Press the "Fn" key to assign the key to a control, but nothing will happen.