'' is not a valid integer value! 错误提示

if MessageDlg(' 是否保存 ？', mtInformation, [mbYes, mbNo], 0) = mrYes then
begin
DataT := formatdatetime('yymmdd',date);
ProNum := DataT+RandToChar;

{ 窗口产生时数据自动保存}
DBChart1.SaveToMetafile(GetExePath +'CollePic\P'+ProNum+'.wmf'); // CollePic\
DB_DBChart2.SaveToMetafile(GetExePath +'CollePic\DB'+ProNum+'.wmf'); // CollePic\

// 将 Access 数据导入到 Excel 中
ADOConnectionAccessToExcel.ConnectionString:='Provider=Microsoft.Jet.OLEDB.4.0;Password="";Data Source='+
GetExePath +'Database\wava.mdb;Persist Security Info=True';
query1.close;
query1.sql.clear;
query1.sql.add('select * from wavetable');
query1.open;


if query1.recordcount <>0 then
begin
ADOConnectionAccessToExcel.execute('Select * Into [Excel 8.0;DATABASE='+GetExePath +'ColleExporttoExcel\'+ProNum+'.XLS].[数据采集] FROM [wavetable]'); //导为 *.xls
ADOConnectionAccessToExcel.close;
end;
{ 结束 窗口产生时数据自动保存}
if not Assigned(ColleInfoForm1) then
begin
ColleInfoForm1:=TColleInfoForm1.create(Application);
ColleInfoForm1.showmodal;
freeandnil(ColleInfoForm1);
end;
end
else
begin
//存储清除
query1.close;
query1.sql.clear;
query1.sql.add('select * from wavetable');
query1.open;
if query1.recordcount<>0 then
begin
query1.close;
query1.sql.clear;
query1.sql.add('delete from wavetable');
query1.ExecSQL;
query1.close;
//==================================================================
// Application.MessageBox('数据成功删除！','提示信息',mb_ok);
//------------------------------------------------------------------
SeriesTimer.Enabled:=False; //时钟置为 0
EditColleTime.Enabled:=true;
//EditColleTime.text:='0';
EditTimeX.text:='0'; //采集源置 0
EditPtY.text:='0';
EditPrY.text:='0';
EditAx.text:='0';
//------------------------------------------------------------------
CollectionQuery.Close;
CollectionQuery.Open;
end
else
begin
exit;
end;
//存储清除

end;

注释： 其中参数ProNum：类型是string
调试错误指示在这行： if MessageDlg(' 是否保存 ？', mtInformation, [mbYes, mbNo], 0) = mrYes then
错误提示是： '' is not a valid integer value!
不知什么原因？希望赐教~`