Unifi widget: Show a more helpful error if specified site not found (#2839)

src/widgets/unifi/component.jsx

@@ -20,6 +20,10 @@ export default function Component({ service }) {
     : statsData?.data?.find((s) => s.name === "default");
 
   if (!defaultSite) {
+    if (widget.site) {
+      return <Container service={service} error={{ message: `Site '${widget.site}' not found` }} />;
+    }
+
     return (
       <Container service={service}>
         <Block label="unifi.uptime" />