Benjamin Berg authored Apr 25, 2018 and Georges Basile Stavracas Neto committed May 02, 2018

When selecting the panel on startup based on the "last-panel" settings,
we need to make sure that the panel exists.

Note that this is a special case which does not use the internal
set_active_panel_from_id API. Using it is currently not possible because
the API does not report back the error and we would end up not selecting
any panel.


(cherry picked from commit f547d912)