Index: openacs-4/packages/adserver/www/adhref.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/adserver/www/adhref.tcl,v
diff -u -N -r1.3 -r1.4
--- openacs-4/packages/adserver/www/adhref.tcl	18 Sep 2002 12:11:28 -0000	1.3
+++ openacs-4/packages/adserver/www/adhref.tcl	12 Feb 2019 18:00:04 -0000	1.4
@@ -89,7 +89,7 @@
     } [adserver_cache_refresh]] {
     set user_id [ad_get_user_id]
     if { $user_id == 0 } {
-        set user_id [db_null]
+        set user_id ""
     } 
     # we know who this user is
     db_dml adv_known_user_insert "