bug#60411: 29.0.60; minibuffer-next-completion skips first candidate when completions-header-format and completion-show-help are nil

[Eli Zaretskii]

> From: Knut Anders Hatlen <kahatlen@gmail.com>
> Date: Thu, 29 Dec 2022 22:25:09 +0100
> 
> 1. Evaluate: (setopt completions-header-format nil completion-show-help nil)
> 
> 2. Type M-x followed by TAB. The *Completions* buffer pops up and shows
> all available commands.
> 
> 3. Type M-<down>.
> 
> Expected result: The first candidate in *Completions* is selected.
> 
> Actual result: The second candidate in *Completions* is selected.

M-<DOWN> runs the command minibuffer-next-completion, so I'm unsure
why you expect what you expect.  It looks like Emacs behaves as
documented here.