Update style.css hide scroll bar when not needed

[Gaz492]

Set overflow to auto in #sidebar_canvas

[thornjad]

Unfortunately some spacing got mixed up with mixed spaces and tabs, but since the fork/branch this PR is coming from no longer exists, we can't make changes now. Since it's stylistic and not functional, in this case I'm going to be fine with it.

In terms of actual functional change, overflow: auto is the correct usage here, thanks for that change! And also good catch on the double semi-colon! That can trip up older browsers.

[HNJAMeindersma]

OMG YES! I've done this myself after installation. Might as well change this in the repo, since the overflow: scroll; option as a default does not make any sense. Yeah ok; it's to have when the table constantly changes between ending right before and after the bottom of your viewport. But it think this not the case for many user in an average receiver location.