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_my_support.dart

@@ -30,7 +30,7 @@ class DesktopMySupport extends StatefulWidget {
 }
 
 class DesktopMySupportState extends State<DesktopMySupport> {
-  List<Ticket> tickets;
+  late List<Ticket> tickets;
 
   double division = 3;
 
@@ -218,7 +218,7 @@ class DesktopMySupportState extends State<DesktopMySupport> {
                 children: <Widget>[
                   Container(
                     child: Text(
-                      ticket.issue.msg,
+                      ticket.issue!.msg,
                       style: TextStyle(
                         fontSize: 19.0,
                       ),
@@ -248,7 +248,7 @@ class DesktopMySupportState extends State<DesktopMySupport> {
                         SizedBox.shrink(),
                         Expanded(
                           child: Text(
-                            S.of(context).followups_token(ticket.followUps.length),
+                            S.of(context).followups_token(ticket.followUps!.length),
                             style: TextStyle(
                               fontSize: 15.0,
                               color: Colors.black87,