add packages, receiving & processing

lib/pages/chat/message_detail.dart

@@ -12,6 +12,7 @@ import 'package:fcs/pages/package/package_info.dart';
 import 'package:fcs/pages/profile/profile_page.dart';
 import 'package:fcs/pages/main/util.dart';
 import 'package:fcs/pages/widgets/bottom_up_page_route.dart';
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
@@ -45,6 +46,10 @@ class MessageDetail extends StatelessWidget {
 
     return Scaffold(
       appBar: AppBar(
+        leading: new IconButton(
+          icon: new Icon(CupertinoIcons.back),
+          onPressed: () => Navigator.of(context).pop(),
+        ),
         backgroundColor: primaryColor,
         elevation: .9,
         title: Text(
@@ -170,6 +175,7 @@ class MessageDetail extends StatelessWidget {
       PackageModel packageModel =
           Provider.of<PackageModel>(context, listen: false);
       Package p = await packageModel.getPackage(message.messageID);
+      if (p == null) return;
       Navigator.push<bool>(context, BottomUpPageRoute(PackageInfo(package: p)));
     }
     if (message.messageType == message_type_profile &&