--- loncom/interface/lonnavmaps.pm	2009/12/03 17:50:42	1.440
+++ loncom/interface/lonnavmaps.pm	2009/12/27 01:31:05	1.441
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Navigate Maps Handler
 #
-# $Id: lonnavmaps.pm,v 1.440 2009/12/03 17:50:42 bisitz Exp $
+# $Id: lonnavmaps.pm,v 1.441 2009/12/27 01:31:05 raeburn Exp $
 
 #
 # Copyright Michigan State University Board of Trustees
@@ -3532,7 +3532,11 @@ sub navHash {
     my $self = shift;
     my $param = shift;
     my $id = shift;
-    return $self->{NAV_MAP}->navhash($param . ($id?$self->{ID}:""));
+    my $arg = $param . ($id?$self->{ID}:"");
+    if (defined($arg)) {
+        return $self->{NAV_MAP}->navhash($arg);
+    }
+    return;
 }
 
 =pod