[Bug]: When variable is used with space after/before brackets their definition is not preserved.

[pszczesniak]

Describe the bug

When there is a declared variable:

:root {
	--foo: red;
}

and is used with some class, for example:

.bar {
	color: var( --foo );
}

In the result the variable declaration is omitted.

All works fine when

.bar {
	color: var(--foo);
}

I know that this is the most common case of how CSS vars are written in CSS code, but the specification does not prohibit the use of spaces.

To Reproduce

Demo on StackBlitz: https://stackblitz.com/edit/stackblitz-starters-g6qdqe?file=index.js,output.css,input.css

Expected Behavior

Used variable is preserved.

Environment

Version: 6.0.0

Add any other context about the problem here

context

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