add quotes to URL functions

lib/single-file/single-file-core.js

@@ -1024,6 +1024,7 @@ this.SingleFileCore = this.SingleFileCore || (() => {
 				if (!DomUtil.testIgnoredPath(resourceURL)) {
 					if (DomUtil.testValidURL(resourceURL, baseURI) && stylesheetContent.includes(urlFunction)) {
 						const { content, indexResource, duplicate } = await batchRequest.addURL(resourceURL);
+						urlFunction = "url(" + JSON.stringify(resourceURL) + ")";
 						const regExpUrlFunction = DomUtil.getRegExp(urlFunction);
 						if (duplicate && options.groupDuplicateImages) {
 							resourceInfos.set(resourceURL, { regExpUrlFunction, dataURI: content, variableName: "var(" + SINGLE_FILE_VARIABLE_NAME_PREFIX + indexResource + ")" });