Index: openacs-4/packages/categories/tcl/category-list-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/categories/tcl/category-list-procs.tcl,v
diff -u -N -r1.10 -r1.10.2.1
--- openacs-4/packages/categories/tcl/category-list-procs.tcl	31 Jan 2018 08:24:28 -0000	1.10
+++ openacs-4/packages/categories/tcl/category-list-procs.tcl	5 Oct 2019 13:02:10 -0000	1.10.2.1
@@ -268,7 +268,7 @@
     }
     set valid_tree_ids ""
     foreach tree_id $tree_ids {
-	if {[lsearch -integer $exclude_tree_ids $tree_id] == -1} {
+	if {$tree_id ni $exclude_tree_ids} {
 	    lappend valid_tree_ids $tree_id
 	}
     }