Use explicit check for included data sources.

src/sbin/sympa.pl.in

@@ -884,9 +884,7 @@ if ($main::options{'dump'} or $main::options{'dump_users'}) {
         exit 1;
     }
 
-    my $result = $list->sync_include();
-
-    if ($result == 0) {
+    unless ($list->has_include_data_sources) {
         printf STDERR "No data sources defined for inclusion into list %s.\n",
             $list->get_id;
         exit 1;