Fix one-off error in patch 4.7.371.

One thing that's been bugging me: When I enter a `NUL` character in neovim (`<C-k>NU` -> `^@`), the text following it renders one space further right than it should. Turns own patch 7.4.353 introduced the bug and 4.7.371 fixed it, except for a slight error in translation. Thank goodness for `git bisect`!