fixed URL generation

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

@@ -1251,7 +1251,7 @@ this.SingleFileCore = this.SingleFileCore || (() => {
 											}
 										});
 									} else {
-										declaration.value = "url(" + DOM.removeQuotes(DomUtil.getCSSValue(content)) + ")";
+										declaration.value = "url(" + content + ")";
 									}
 								}
 							}