Ошибка: Class does not have a default property

interface
 
uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, Grids;
 
type
  TSDIAppForm = class(TForm)
    StringGrid1: TStringGrid;
    StringGrid2: TStringGrid;
    StringGrid3: TStringGrid;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Button1: TButton;
    StringGrid4: TStringGrid;
    Label4: TLabel;
    StringGrid5: TStringGrid;
    Label5: TLabel;
    Label6: TLabel;
    StringGrid6: TStringGrid;
    Label7: TLabel;
 
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  SDIAppForm: TSDIAppForm;
  T:Boolean;
  G:Real;
implementation
 
uses About;
 
{$R *.dfm}
Function MinKom(Name:TStringGrid):integer;
var i,minim:integer; p:real;
begin
  With Name do
  begin
    p:= StrToFloat(Name[1]);
    minim:=1;
    for i := 1 to ColCount-1 do
    begin
      if StrToFloat(Name[i])<p then begin
        p:=StrToFloat(Name[i]);
        minim:=i;
      end;
 
    end;
 
  end;
  MinKom:=minim;
end;
 
 
procedure TSDIAppForm.Button1Click(Sender: TObject);
var i,j:integer;
begin
 
  for i := 1 to MinKom(StringGrid2)-1 do begin
  G:=StrToFloat(StringGrid2[1,i]);
  StringGrid5.Cells[1,i]:=FloatToStr(G*G)
  end;
  if MinKom(StringGrid3)<=3 then T:=true else T:=False;
  if T=True then
  StringGrid4.Cells[1,1]:='True' else StringGrid4.Cells[1,1]:='False';
  StringGrid6.Cells[1,1]:=IntToStr(MinKom(StringGrid1));
 
end;
 
end.

G:=StrToFloat(StringGrid2.Cells[1,i]);