phase3: nullfix arg-bang handler (argument_type/invalid_assignment). 872 -> 621

lib/widgets/mobile/mobile_plain_page.dart

@@ -28,7 +28,7 @@ class MobilePlainPageState extends State<MobilePlainPage> {
       padding: EdgeInsets.only(top: 20, left: 16.0, right: 16.0, bottom: 16.0),
       child: Center(
         child: Text(
-          widget.blog.title,
+          widget.blog.title!,
           style: TextStyle(
             fontWeight: FontWeight.bold,
             fontSize: 20,
@@ -40,7 +40,7 @@ class MobilePlainPageState extends State<MobilePlainPage> {
       padding: EdgeInsets.only(left: 16.0, right: 16.0, bottom: 20.0),
       child: MarkdownBody(
         shrinkWrap: true,
-        data: widget.blog.body,
+        data: widget.blog.body!,
       ),
     ));
 
@@ -52,7 +52,7 @@ class MobilePlainPageState extends State<MobilePlainPage> {
             Navigator.of(context).pop();
           },
         ),
-        title: Text(widget.blog.title),
+        title: Text(widget.blog.title!),
         backgroundColor: Theme.of(context).primaryColor,
       ),
       body: SingleChildScrollView(