[Delphi] TTreeView a CustomSort

Zdravim,
mam problem s TTreeview a CustomSort. V treeview mam napr:

Kód:

---

- kalendar
+- 2005
+- 2006
+- 2007

01 function serad(Node1,Node2: ttreeview; data: integer): integer;
02 begin
03  result:=strtoint(Node1.text)-strtoint(Node2.text);
04 end;
05
06 procedure Form1.Button1Click(Sender: TObject);
07 var node: TTreeNode;
08 begin
09  node:=TreeView1.Items.GetFirstNode; // dostanu Kalendar
10  node:=node.getFirstChild; // dostanu 2005
11  node.CustomSort(@serad,0); // seradi
12 end;

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tohle funguje v pohode.
ale kdyz pridam dalsi treenode k jednomu z tech roku:

Kód:

---

- kalendar
+- 2005
  +- leden
  +- unor
+- 2006
+- 2007

---

tak to hazi na radku 4 chybu "access violation at ... Read of address 00000008".

Urcite to bude naka lamarina. Dik za reakce...