[Lazarus] Exception when re-opening a modal dialogue

[Timothy Groves]

So when I call TfrmNewChapter.ShowModal, it works the first time. But 
when I call it the second time, I get an exception.  The form is closed 
with the OK or Cancel buttons;  their methods are given below.  What am 
I doing wrong?


procedure TfrmNewChapter.btnCancelClick(Sender: TObject);
begin
   txtChapterTitle.Text := '';
   frmNewChapter.Hide;
end;

procedure TfrmNewChapter.btnOKClick(Sender: TObject);
var
   s : string;
begin
   if (txtChapterTitle.Text <> '') then begin
     NewChapter (txtChapterTitle.Text);
     txtChapterTitle.Text := '';
     str (ChapterCount, s);
     while (length (s) < 4) do
         s := '0' + s;
     Chapter^.Filename := Story^.ShortName + s;
     PopulateChapterList;
     frmNewChapter.Hide;
     MarkChapterListDirty;
   end;
end;