Hello,

I wanted to mark certain filenames as images and added this to my config.el:

(add-to-list 'image-file-name-regexps "/preview/")

But when I run `org-toggle-inline-images` now, I get the following error.

image-file-name-regexp: Wrong type argument: characterp, "/preview/"

Even though it says:
```lisp
image-file-name-regexps is a variable defined in image-file.el.gz.

Value
("/preview/")

Documentation
List of regexps matching image-file filenames.
```And the variable is clearly a list.

As posted in [https://emacs.stackexchange.com/questions/72902/image-file-name-regexp-wrong-type-argument-characterp](https://emacs.stackexchange.com/questions/72902/image-file-name-regexp-wrong-type-argument-characterp?noredirect=1#comment118105_72902)

Best,
Janek