The sidebar hides the main panel
When enabled, the sidebar hides the main panel, so that it is not possible to use the application while showing the sidebar.
This is caused by the fact that the first time the application runs, it creates a window state file (cache in the user home dir, g_key_file) with a sidebar_width equal to zero.
See the original bug report: https://bugzilla.gnome.org/show_bug.cgi?id=788621
Might also be related to: https://bugzilla.gnome.org/show_bug.cgi?id=395126