[bug]ExcelBase::convertToColName

[MonostableLSD]

当data是26的整数倍时，mode= data % 26 == 0，导致转换出“@”字符，导致表格保存失败。

[MonostableLSD]

/// \brief 把列数转换为excel的字母列号
/// \param data 大于0的数
/// \return 字母列号，如1->A 26->Z 27 AA
///
void ExcelBase::convertToColName(int data, QString &res) //keep data 1-26
{
    Q_ASSERT(data>0 && data<65535);
    int a = (data-1) / 26 ;
    if(a > 0)
    {
        int b = (data-1) % 26 +1;
        convertToColName(b,res);
        convertToColName(a,res);
    }
    else
    {
        res=(to26AlphabetString(data)+res);
    }
}

微软的喂饭写法：

Function ConvertToLetter(iCol As Long) As String
   Dim a As Long
   Dim b As Long
   a = iCol
   ConvertToLetter = ""
   Do While iCol > 0
      a = Int((iCol - 1) / 26)
      b = (iCol - 1) Mod 26
      ConvertToLetter = Chr(b + 65) & ConvertToLetter
      iCol = a
   Loop
End Function