[Select] Unselect / Toggle select is not visually working (background remains)

[caub]

Steps to Reproduce (for bugs)

https://codesandbox.io/s/7jox7jylj6

• select a value
• click it again, to unselect it
• then the option doesn't lose the selected background until the select menu is closed and reopened

So we can't know if we have unselect it

Expected Behavior

It should toggle selection on a item after each click

This happens with multiple option at least

edit: actually the font-weight is slightly changing (400 / 500), but I believe this background should be cleared is the pointer leaves hover, I guess there's an :active rule that still make it with this background

Current Behavior

Unselected items stay visually selected

Your Environment

Tech	Version
Material-UI	1.0.0-beta.24
React	16.2.0
browser	chrome, firefox

[oliviertassinari]

then the option doesn't lose the selected background until the select menu is closed and reopened

Duplicate of #5186