Sidebars don't restore if you have any sidebars on the right side of the dockpanel

[telamonian]

Having any sidebars on the right side of the dock panel seems to break the restorer. Starting from any of:

on reload all sidebars are closed, regardless of initial state:

The expected behavior is that both sidebars should be restored to their pre-reload state.

[jasongrout]

After applying #7242 on master, for me the left sidebar correctly restores always, but the right sidebar always starts out closed.

[jasongrout]

Oh, actually when I have filebrowser on the right and running tab showing on the left, the left restores correctly and the right doesn't.

When I have your setup, with cell tools on the right and filebrowser on the left, I see what you see.