phase3: nullable fields/methods, casts, ?.call, pinput/YoutubePlayer v5, buttonColor, dead-code removal. 72->16

lib/widgets/desktop/desktop_blog.dart

@@ -34,7 +34,7 @@ class DesktopBlog extends StatefulWidget {
 }
 
 class DesktopBlogState extends State<DesktopBlog> {
-  late List<Blog> blogs;
+  List<Blog>? blogs;
 
   double division = 2;
 
@@ -49,7 +49,7 @@ class DesktopBlogState extends State<DesktopBlog> {
   void _onRefresh() {
     _page = 1;
     if (blogs != null) {
-      blogs.clear();
+      blogs!.clear();
     } else {
       blogs = [];
     }
@@ -98,7 +98,7 @@ class DesktopBlogState extends State<DesktopBlog> {
         enablePullUp: true,
         header: WaterDropHeader(),
         footer: CustomFooter(
-          builder: (BuildContext context, LoadStatus mode){
+          builder: (BuildContext context, LoadStatus? mode){
             Widget footer;
             if(mode == LoadStatus.idle) {
               footer = Text(S.of(context).pull_up_to_load_more);
@@ -148,9 +148,9 @@ class DesktopBlogState extends State<DesktopBlog> {
             right: 8.0,
           ),
           child: blogs == null ? Text('') :
-          (blogs.length > 0 ?
+          (blogs!.length > 0 ?
           Wrap(
-            children: blogs.map((a) => GestureDetector(
+            children: blogs!.map((a) => GestureDetector(
               child: _getBlog(a),
               onTap: () {
                 Routes.router.navigateTo(context, '/view-blog/${a.id}');
@@ -293,7 +293,7 @@ class DesktopBlogState extends State<DesktopBlog> {
           if (blogs == null) {
             blogs = [];
           }
-          blogs.addAll((value['blogs'] as List).map((e) => Blog.fromJson(e)).toList());
+          blogs!.addAll((value['blogs'] as List).map((e) => Blog.fromJson(e)).toList());
         });
       }
     }).catchError((error) {