[zsh bug report] vi-change-whole-line does not kill whole line in some cases

[Kuba <lxkuba@xxxxx>]

Hi,

I believe I found a bug in `vi-change-whole-line`.

Minimal zshrc allowing to reproduce the issue:

```

bindkey -v

```

## Steps to reproduce:

1. type 2 words, for example `word1 word2`

2. enter vicmd mode and move cursor to the beginning of first word (`esc` `0`)

3. use `vi-change` to change word then go back to vicmd (`c` `w` `esc`)

4. use `vi-change-whole-line`

## Expected result:

Kill the current line and enter insert mode.

## Actual result:

The line is killed but the cursor is positioned one place to the right making the line not empty (line contains single space)

I attach gif recording presenting the issue.

zsh version: 5.6.2 (x86_64-debian-linux-gnu)

All the best,

Kuba

Attachment: zsh_bug1.gif
Description: GIF image