ui: Fix mutated nspace argument (#9222)

ui/packages/consul-ui/app/components/topology-metrics/stats/index.js

@@ -14,10 +14,11 @@ export default class TopologyMetricsStats extends Component {
     } else {
       // For up/downstreams we need to pull out the stats for the service we
       // represent.
-      if ((this.args.nspace || '').length === 0) {
-        this.args.nspace = 'default';
+      let nspace = this.args.nspace || '';
+      if (nspace.length === 0) {
+        nspace = 'default';
       }
-      let entity = `${this.args.item}.${this.args.nspace}.${this.args.dc}`;
+      let entity = `${this.args.item}.${nspace}.${this.args.dc}`;
       this.stats = event.data.stats[entity];
     }
     // Limit to 4 metrics for now.