ensure the list is non-empty

kamailio/dispatcher-role.cfg

@@ -65,7 +65,7 @@ route[DISPATCHER_FIND_ROUTES]
     }
     #!endif
 
-    if (!ds_select_dst("$var(ds_group)", "0")) {
+    if (!ds_select_dst("$var(ds_group)", "0") || $(avp(ds_dst)[0]) == $null) {
         # if we selected from group 1, try again in group 2
         if ($var(ds_group) == 1) {
                 if (!ds_select_dst("2", "0")) {