del-header removes empty cells when the input is one column

[alvanuffelen]

Prerequisites

• [x] make sure you're are using the latest version by csvtk version
• [x] read the usage

Describe your issue

csvtk del-header on one column removes the empty cells. example.txt

Empty cells are included:

cat example.txt | csvtk cut -f species

Empty cells are removed:

cat example.txt | csvtk cut -f species | csvtk del-header

[shenwei356]

Hmm, they are treated as empty rows and skipped since v0.26.0.

This is problematic in your situation, I should make it optional with

 -E, --ignore-empty-row       ignore empty rows

[shenwei356]

That's sad, the official csv reader skip blank lines by default, and no option to disable this.

https://pkg.go.dev/encoding/csv

Blank lines are ignored. A line with only whitespace characters (excluding the ending newline character) is not considered a blank line.

Some guys tried to change this but failed., the PR was not accepted.

[shenwei356]

A workaround way: add the row number with the global flag -Z/--show-row-num, which would stop del-header removing blank lines

$ cat example.txt | csvtk cut -f species -Z | csvtk del-header | csvtk cut -f  -1 | wc -l
162

$ cat example.txt | wc  -l
163