configure.ac: fix have_dbus if dbus support is disabled

If dbus support is explicitly disabled, $have_dbus should be no, but was
empty. systemd-login support depends on dbus, but the check does not
trigger correctly, if $have_dbus is empty.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
1 file changed