`clean-css`: Incorrect output if a whitespace is placed after a custom fragment

Given below config:
```js
{ minifyCSS: true, ignoreCustomFragments: [ /{{[#^\/]?.*?}}/ ] }
```
results in:
```html

```
(demo: https://replit.com/@lemnis/htmlmin#index.js)

---

The issue doesn't exist if the space between `}}` and `display` is removed or if the semicolon is placed after the second custom fragment.

Reproduce the issue with the JavaScript configuration and example from the linked Replit demo, focusing on minifyCSS handling of ignoreCustomFragments. Trace the custom-fragment and whitespace processing, then verify that the output preserves both fragments and removes only the intended whitespace as shown in the expected HTML.

Written by the indexing model from the issue text.