phase3: nullfix.py batch script — bang/late/param-nullable

Automated null-safety fixes driven by dart analyze (no corruption):
- unchecked_use_of_nullable_value: insert '!' on receiver (property/method/[]/op)
- not_initialized field/var: mark 'late'
- missing_default_value_for_parameter: nullable param
Errors: 2374(peak) -> 907

lib/widgets/desktop/desktop_me.dart

@@ -16,9 +16,9 @@ import '../../utils/util_web.dart'
     if (dart.library.io) '../../utils/util_io.dart';
 import '../../utils/utils.dart';
 
-MediaQueryData mediaQuery;
-double statusBarHeight;
-double screenHeight;
+late MediaQueryData mediaQuery;
+late double statusBarHeight;
+late double screenHeight;
 
 class DesktopMe extends StatefulWidget {
   final Key? key;
@@ -32,11 +32,11 @@ class DesktopMe extends StatefulWidget {
 }
 
 class DesktopMeState extends State<DesktopMe> {
-  int userId;
-  String accessToken;
+  late int userId;
+  late String accessToken;
 
-  bool isLoading;
-  User _user;
+  late bool isLoading;
+  late User _user;
 
   double sideSpace = 0;
   double mainSpace = 1200;
@@ -81,7 +81,7 @@ class DesktopMeState extends State<DesktopMe> {
           children: <Widget>[
             Container(
               margin: EdgeInsets.only(right: 5.0),
-              child: _user != null && _user.avatarUrl.isNotEmpty
+              child: _user != null && _user.avatarUrl!.isNotEmpty
                   ? Util.showImage(
                       'https:${_user.avatarUrl}',
                       width: 60,
@@ -182,7 +182,7 @@ class DesktopMeState extends State<DesktopMe> {
                                 Container(
                                   child: Text(
                                     _user != null
-                                        ? '${_user.wallet.toStringAsFixed(2)}'
+                                        ? '${_user.wallet!.toStringAsFixed(2)}'
                                         : '0.00',
                                     style: TextStyle(
                                       fontSize: 24.0,