Found **NullReferenceException** when trying insert rows into copied sheet.
```
class Program
{
static void Main(string[] args)
{
XLWorkbook wbk = new XLWorkbook(@"C:\MySheet.xlsx");
IXLWorksheets shts = wbk.Worksheets;
IXLWorksheet sht = shts.First();
sht.CopyTo("new_sheet");
sht = shts.Last();
sht.Row(1).InsertRowsBelow(1);
wbk.Save();
}
```
Comments: Please try the latest version of ClosedXML (v0.87.1 at this stage). If you still experience the issue, log it on the new GitHub page.
```
class Program
{
static void Main(string[] args)
{
XLWorkbook wbk = new XLWorkbook(@"C:\MySheet.xlsx");
IXLWorksheets shts = wbk.Worksheets;
IXLWorksheet sht = shts.First();
sht.CopyTo("new_sheet");
sht = shts.Last();
sht.Row(1).InsertRowsBelow(1);
wbk.Save();
}
```
Comments: Please try the latest version of ClosedXML (v0.87.1 at this stage). If you still experience the issue, log it on the new GitHub page.