Fix serializing CSSNamespaceRule with omitted prefix

Author: cdoublev

lib/cssom/CSSNamespaceRule-impl.js

@@ -1,5 +1,5 @@
 
-import { serializeIdentifier, serializeURL } from '../serialize.js'
+import { serializeComponentValue, serializeURL } from '../serialize.js'
 import CSSRuleImpl from './CSSRule-impl.js'
 import { isFunction } from '../utils/value.js'
 
@@ -17,7 +17,7 @@ export default class CSSNamespaceRuleImpl extends CSSRuleImpl {
         super(globalObject, args, privateData)
         const { prelude: [prefix, location] } = privateData
         this.namespaceURI = isFunction(location) ? location.value[0].value : location.value
-        this.prefix = serializeIdentifier(prefix)
+        this.prefix = serializeComponentValue(prefix)
     }
 
     /**