fix: the vi-paste-before command in line-mode at the last line should open a newline before current line.

[sakurawald]

This commit fix the edge case when vi-paste a line before at the last line.

Taken this example buffer

first
second
third1 th[i]rd2 third 3

If current-line is at the last line, then the vi-paste-before command in line-mode should open a new line above current-line.

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The keypoint is that: The last line doesn't contains the line-break character, so it's an edge-case.

[sakurawald]

This commit still can't pass the continous paste before case.
If in line-mode paste, the paste string contains a line-break character, this line-break character introduces the difference between the last line and not the last line.

[sakurawald]

The vi-paste-before and vi-paste-after commands works well, if current line is not the last line.

An exapmle buffer is:

first
second
third1 th[i]rd2 third 3
end

[sakurawald]

The vi-yank-line command, behaves differently on the last line and not the last line.
In not the last line, the line-break character is copied.
In the last line, the line-break character is not copied.