bug#72176: 30.0.60; icomplete-vertical-mode failed to work with Error

[Eli Zaretskii <eliz@gnu.org>]

> From: Eason Huang <aqua0210@foxmail.com>
> Date: Thu, 18 Jul 2024 20:13:21 +0800
> 
> I tried to use icomplete-vertical-mode, but it doesn't works with
> Emacs 30.0.60 and Emacs 31.0.50.
> 
> when trying `C-x C-f ~/` and input the first character of the names of
> folders under home directory, will get bellow error:
> ```
> Error in post-command-hook (icomplete-post-command-hook): (wrong-type-argument number-or-marker-p nil)
> ```
> 
> steps to reproduce:
> 
> 1. start Emacs with `emacs -Q`
> 2. `M-x icomplete-vertical-mode` enable icomplete-vertical-mode
> 3. try to open some file under the directory under Home directory
>    such as: `C-x C-f ~/` and then input the name a directory,
>    here I will input `t` charactor, because I have the tmp folder.
> 
> 4. Now you will get the error:
> 
> ```
> Error in post-command-hook (icomplete-post-command-hook): (wrong-type-argument number-or-marker-p nil)
> ```

I cannot reproduce this, but I'm not on macOS.