--- loncom/homework/lonsimpleproblemedit.pm	2006/06/30 01:16:41	1.19
+++ loncom/homework/lonsimpleproblemedit.pm	2009/02/01 20:40:28	1.20
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Simple Problem Parameter Setting "Editor"
 #
-# $Id: lonsimpleproblemedit.pm,v 1.19 2006/06/30 01:16:41 albertel Exp $
+# $Id: lonsimpleproblemedit.pm,v 1.20 2009/02/01 20:40:28 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -143,13 +143,16 @@ ENDFOIL
 sub get_parent_uri {
     my ($cur_symb)=@_;
     my $navmap = Apache::lonnavmaps::navmap->new();
-    my $it = $navmap->getIterator(undef, undef, undef, 1);
-    while ( my $res=$it->next()) {
-	if (ref($res) &&  $res->symb() eq  $cur_symb) { last; }
-    }
-    my ($src,$symb,$anchor)=&Apache::lonnavmaps::getLinkForResource($it->getStack());
-    if (defined($anchor)) { $anchor='#'.$anchor; }
-    return $src.'?symb='.&escape($symb).$anchor;
+    if (defined($navmap)) {
+        my $it = $navmap->getIterator(undef, undef, undef, 1);
+        while ( my $res=$it->next()) {
+	    if (ref($res) &&  $res->symb() eq  $cur_symb) { last; }
+        }
+        my ($src,$symb,$anchor)=&Apache::lonnavmaps::getLinkForResource($it->getStack());
+        if (defined($anchor)) { $anchor='#'.$anchor; }
+        return $src.'?symb='.&escape($symb).$anchor;
+    }
+    return;
 }
 
 sub handler {
@@ -219,8 +222,14 @@ sub handler {
 					     $spell_header));
     if ($symb) {
 	$r->print('<h1>'.&Apache::lonnet::gettitle($symb).'</h1>');
-	$r->print('<table width="100%" bgcolor="#FFFFAA" border="2"><tr><td>'.
-                '<a href="'.&get_parent_uri($symb).'">'.&mt('Student View').'</a> - '.&mt('Note: it can take up to 10 minutes for changes to take effect for all users.').
+	$r->print('<table width="100%" bgcolor="#FFFFAA" border="2"><tr><td>');
+        my $displaylink = &get_parent_uri($symb);
+        if ($displaylink ne '') {      
+            $r->print('<a href="'.$displaylink.'">'.&mt('Student View').'</a> - ');
+        } else {
+            $r->print('<span class="LC_error">'.&mt('An error occurred retrieving the link to this problem').'<br />'.&mt('You may need to [_1]re-select the course[_2] and then return to this resource to view it.','<a href="/adm/roles">','</a>').'</span><br />'); 
+        }
+        $r->print(&mt('Note: it can take up to 10 minutes for changes to take effect for all users.').
 		  &Apache::loncommon::help_open_topic('Caching').'</td></tr></table>');
 	$r->print('<table border="2" bgcolor="#FFFFFF" width="100%"><tr><td>'.
                   &rawrendering($symb).