use if for checking ink

Author: aminya

lib/ui.js

@@ -45,9 +45,10 @@ export default {
         this.notifications.show("Client Connected");
       })
     );
-    this.subs.add(this.client.onDetached(() => {
-        // TODO do we need this optional chaining check?
-        this.ink && this.ink.Result && this.ink.Result.invalidateAll()
+    subs.add(client.onDetached(() => {
+        if (ink) {
+          ink.Result.invalidateAll()
+        }
       })
     );
   },