Sidebar does not display multi-column tiling until adjusted

[wbrenna]

If the sidebar is set to a width large enough to allow for e.g. two columns of pages and preferences are saved, upon reopening, only one column is rendered until the window is adjusted.

[x2b]

The reason is that at the time the file is loaded the MainWindow has not been show()n yet, hence the geometry is unknown. Therefore the alignment does not work in that case. This seems to be doing the trick:

x2b@f9b9263

[wbrenna]

Thanks! I've patched that in.