When using DuplicateRow, it is not duplicated correctly when there are multiple merged cells.

[yuki2006]

Description

When duplicating a row with multiple merged cells, the cells that are used correctly are not copied.

Perhaps this i++ skips the loop step.

https://github.com/360EntSecGroup-Skylar/excelize/blob/77978ac68d3808060e58df41ebede4b9f3631641/rows.go#L605

Steps to reproduce the issue:
1.

	f, err := excelize.OpenFile("../../.ignore/B.xlsx")
	if err != nil {
		panic(err)
	}
	sheet := f.GetSheetName(0)
	err = f.DuplicateRowTo(sheet, 1, 3)
	if err != nil {
		panic(err)
	}
	err = f.SaveAs("../../.ignore/B_.xlsx")
	if err != nil {
		panic(err)
	}

Describe the results you received:

Describe the results you expected:

Want the same thing as the 1 col to be the 3 col.

Output of go version:

go 1.15

Excelize version or commit ID:

77978ac68d3808060e58df41ebede4b9f3631641

[xuri]

Thanks for your issue. I have fixed it, please try to use the master branch code, and this patch will be released in the next version.