fix single conversation example

example/lib/single_conversation.dart

@@ -52,12 +52,15 @@ class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      home: StreamChat(
-        client: client,
-        child: StreamChannel(
-          channel: channel,
-          child: ChannelPage(),
-        ),
+      builder: (context, widget) {
+        return StreamChat(
+          child: widget,
+          client: client,
+        );
+      },
+      home: StreamChannel(
+        channel: channel,
+        child: ChannelPage(),
       ),
     );
   }

example/pubspec.yaml

@@ -1,6 +1,6 @@
 name: example
 description: A new Flutter project.
-version: 1.0.20+21
+version: 1.0.21+22
 
 environment:
   sdk: ">=2.2.2 <3.0.0"