aerc.SelectedAccount() is used in lots of places. Most of them without
checking the return value.
In some cases, the currently selected tab is not related to any account
(widget.Terminal for example). This can lead to unexpected crashes when
accessing account specific configuration.
When possible, return an error when no account is currently selected.
If no error can be returned, fallback to non-account specific
configuration.
Signed-off-by: Robin Jarry <robin@jarry.cc>
Reviewed-by: Koni Marti <koni.marti@gmail.com>
c26d08103b