Initialize variables later

scripts/postcss/css-url-to-variables.js

@@ -15,12 +15,13 @@ limitations under the License.
 */
 
 const valueParser = require("postcss-value-parser");
+
 /**
  * This plugin extracts content inside url() into css variables.
  * The extracted css variables are added to the :root section.
  */
 let counter;
-const urlVariables = new Map();
+let urlVariables;
 const idToPrepend = "icon-url";
 
 function extractUrl(decl) {
@@ -58,6 +59,7 @@ function addResolvedVariablesToRootSelector(root, { Rule, Declaration }) {
  * @type {import('postcss').PluginCreator}
  */
 module.exports = (opts = {}) => {
+    urlVariables = new Map();
     counter = 0;
     return {
         postcssPlugin: "postcss-url-to-variable",