bug#53203: Comment with lots of color codes crashes or hangs emacs in scss-mode

[Colin]

Hi,


I have the following snippet in example.scss file:

```

/*
#ffffff #ffffff
#ffffff #ffffff
#ffffff #ffffff
#ffffff #ffffff
#ffffff #ffffff
*/
```

On opening the file with emacs -Q (27.1 and a fresh build of git master 
(29.0.50), emacs hangs.

If I remove one/two lines, it appears to burn some CPU and then work, so 
it looks like an exponential search or something.

For now I'll remove the snippet from my code, but an interesting bug 
nonetheless ;)