in jsgantt, only the first parent matters as it only supports single parent.

so if it's not the first parent, folder doesn't work.
here we make a more strict "has_members" testing to avoid invalid "folder" chars

lib/RT/Extension/JSGantt.pm

@@ -155,6 +155,21 @@ sub TicketsInfo {
         }
 
         my $has_members = $Ticket->Members->Count ? 1 : 0;
+        if ($has_members) {
+
+           # need to examine more as it may not the first parent of it's members
+            my $members = $Ticket->Members;
+            my $indeed_has_members;
+            while ( my $member = $members->Next ) {
+                if ( $member->BaseObj->MemberOf->First->TargetObj->id == $Ticket->id )
+                {
+                    $indeed_has_members = 1;
+                    last;
+                }
+            }
+
+            $has_members = $indeed_has_members || 0;
+        }
 
         my $depends = $Ticket->DependsOn;
         my @depends;