list index out of bounds(1)

unit Formcount;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, StdCtrls, Grids, DBGrids, ComCtrls, Buttons, ToolWin,
  DB, ADODB;type
  TForm11 = class(TForm)
    Panel1: TPanel;
    ToolBar1: TToolBar;
    BitBtn1: TBitBtn;
    BitBtn2: TBitBtn;
    BitBtn3: TBitBtn;
    BitBtn4: TBitBtn;
    ToolButton1: TToolButton;
    BitBtn5: TBitBtn;
    BitBtn6: TBitBtn;
    BitBtn7: TBitBtn;
    ToolButton2: TToolButton;
    BitBtn8: TBitBtn;
    BitBtn9: TBitBtn;
    ToolButton3: TToolButton;
    BitBtn10: TBitBtn;
    DBGrid2: TDBGrid;
    Bevel4: TBevel;
    Label1: TLabel;
    Label2: TLabel;
    ComboBox1: TComboBox;
    Button2: TButton;
    Label3: TLabel;
    Edit1: TEdit;
    DataSource1: TDataSource;
    ADOQuery1: TADOQuery;
    DBGrid1: TDBGrid;
    ComboBox2: TComboBox;
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure ComboBox2Change(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form11: TForm11;implementation
uses FormKaoQin;
{$R *.dfm}procedure TForm11.FormCreate(Sender: TObject);
begin
 try
    if (Screen.Width=800) and (Screen.Height=600) then
    begin
      Form10.Left:=0;
      Form10.Width:=649;
      Form10.Top:=0;
      Form10.Height:=638;
    end;
    if (Screen.Width=1024) and ( Screen.Height=768) then
    begin
      Form10.Width:=649;
      Form10.Height:=638;
      Form10.Position:=poDesktopCenter;
    end;
  except
    Application.MessageBox('请正确选择屏幕分辨率：1024X768 或 800X600 !','提示！',0+64);
    exit;
  end;
end;procedure TForm11.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Form10.Visible:=true;
  Form11.Hide;
end;procedure TForm11.ComboBox2Change(Sender: TObject);
var
temp:string;
sqlstr:string;
begin
  temp:=trim(combobox2.text) ;
  sqlstr := 'select * from ' + temp ;
  ADOQuery1.active := false;
  ADOQuery1.SQL.Clear;
  ADOQuery1.SQL.Add(sqlstr);
  ADOQuery1.active :=true;
  dbgrid1.Columns[0].Width:=80;
  dbgrid1.Columns[1].Width:=60;
  dbgrid1.Columns[2].Width:=180;
  dbgrid1.Columns[3].Width:=50;end;end.
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运行后出现问题是：list index out of bounds(1).这个究竟是什么原因？怎么解决呢