Hi there, I noticed that after this commit

There are some changes in the function `shr-heading`.

```diff

(defun shr-heading (dom &rest types)

(shr-ensure-paragraph)

- (apply #'shr-fontize-dom dom types)

+ (let ((start (point))

+ (level (string-to-number

+ (string-remove-prefix "shr-h" (symbol-name (car types))))))

+ (apply #'shr-fontize-dom dom types)

+ (put-text-property start (pos-eol) 'outline-level level))

(shr-ensure-paragraph))

```

In racket-mode, when looking for local docs, racket-mode will use the

following function to `shr-heading`:

(shr-heading dom face)

Here `dom` is unrelated to this, problem occurs in `face`:

`racket-mode` passed `face` (as an example, which value is

`(variable-pitch (:height 1.6))`) to `shr-heading`, when `shr-heading`

parses it:

(symbol-name (car '((variable-patch (:height 1.6)))))

error occurs:

(wrong-type-argument symbolp (variable-patch (:height 1.6)))

Does this counts as an Emacs's bug, or racket-mode's problem? thx