Comment 9 for bug 1316862

Reproduced the bug (I think, though I'm doubting whether I moved the mouse across the top panel now...). The bug doesn't exist in Unity 7.4.5+16.04.20171201.3 so I think the fix works. I can't see any obvious regressions (fiddled around a bit with the lock screen), though switching accounts doesn't work properly after I installed `ubuntu-mate-desktop` so maybe I can't test as thoroughly as someone with a clean system can.