Just a small protection, the column might not exist at this point

Author: davidberneda

demos/VirtualData/Array/Unit_Array.dfm

@@ -49,7 +49,7 @@ object FormArray: TFormArray
       OnClick = Button1Click
     end
     object BInteger: TButton
-      Left = 280
+      Left = 282
       Top = 8
       Width = 75
       Height = 25

demos/VirtualData/Array/Unit_Array.pas

@@ -234,9 +234,12 @@ procedure TFormArray.SetExpander(const AColumn:String; const ARows:TRows);
 begin
   tmp:=TeeGrid1.Columns[AColumn];
 
-  tmp.Render:=TExpanderRender.Create(tmp.Changed);
+  if tmp<>nil then
+  begin
+    tmp.Render:=TExpanderRender.Create(tmp.Changed);
 
-  TExpanderRender(tmp.Render).OnGetExpanded:=ARows.IsChildrenVisible;
+    TExpanderRender(tmp.Render).OnGetExpanded:=ARows.IsChildrenVisible;
+  end;
 end;
 
 // Create a new Title grid-band