Index: openacs-4/packages/simulation/tcl/template-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/simulation/tcl/template-procs.tcl,v
diff -u -r1.75 -r1.76
--- openacs-4/packages/simulation/tcl/template-procs.tcl	9 May 2018 15:33:33 -0000	1.75
+++ openacs-4/packages/simulation/tcl/template-procs.tcl	12 Feb 2019 18:00:04 -0000	1.76
@@ -82,7 +82,7 @@
                     switch $attr {
                         suggested_duration {
                             if { [empty_string_p $row($attr)] } {
-                                set $varname [db_null]
+                                set $varname ""
                             } else {
                                 # TODO B: need better tests for duration before passing it into the database.
                                 set $varname "interval '[db_quote $row($attr)]'"