dbus: Move send_message() call before _error label
Commit
09e6818d01 changed dbus server paths so requests fell back
to freeing allocated memory on errors. However certain kinds of
dbus replies issue a final g_dbus_connection_send_message() there.
In case of errors, _reply_message will be NULL, and the error paths
would have already issued g_dbus_method_invocation_return_gerror(),
so the g_dbus_connection_send_message() call is both unnecessary and
warns on the NULL argument. So move the DBus reply before the _error
label.
https://bugzilla.gnome.org/show_bug.cgi?id=778540