Wiki sidebar/table of contents is not scrollable

[gonX]

The bottom contents of the table of contents (ToC) are cut off until the page is scrolled to bottom on wiki pages

How to reproduce:

1. Open any wiki page with many entries in the ToC (e.g. General FAQ)
2. Zoom the page, or shrink the window vertically, until the ToC is cut off
3. Attempt to scroll on the ToC area, and observe that the ToC is not scrolled, but the page is, until you've scrolled to the bottom of the page

Instead, the ToC should somehow be scrollable independently of the contents.

This is currently mostly an issue on smaller monitors, or users with high zoom/DPI levels, but will become a general problem if the ToC receives a significant amount of entries.