Environment

• clean-css version - npm ls clean-css: 5.2.0
• node.js version - node -v: v14.17.0
• operating system: Ubuntu 20

Configuration options

CLI:

cleancss -O2 --format minify

Input CSS

.test {--tw-blur: var(--tw-empty,/*!*/ /*!*/);}

Actual output CSS

.test{--tw-blur: var(--tw-empty,);/*!*//*!*/}

Expected output CSS

.test {--tw-blur: var(--tw-empty,/*!*/ /*!*/);}

I thought the latest PR should have fixed it but it seems to have the same issue.