Index: openacs-4/packages/news-aggregator/www/aggregator-delete.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/news-aggregator/www/aggregator-delete.tcl,v
diff -u -r1.5 -r1.6
--- openacs-4/packages/news-aggregator/www/aggregator-delete.tcl	9 Apr 2018 14:27:02 -0000	1.5
+++ openacs-4/packages/news-aggregator/www/aggregator-delete.tcl	10 Apr 2018 08:10:29 -0000	1.6
@@ -17,7 +17,8 @@
     # We are deleting the user's default aggregator
     # Set user's oldest aggregator as new default
     set new_default_aggregator [db_string select_oldest_aggregator {} -default ""]
-    if { $new_default_aggregator ne "" } {
+    # Test if the variable whose *name* is assigned to new_default_aggregator, exists and is not empty
+    if { [info exists $new_default_aggregator] && [set $new_default_aggregator] ne "" } {
         news_aggregator::aggregator::set_user_default \
             -user_id $user_id \
             -aggregator_id $new_default_aggregator