Make a few values non-nullable in cupertino (#119478)

packages/flutter/lib/src/cupertino/route.dart

@@ -1010,14 +1010,12 @@ class CupertinoModalPopupRoute<T> extends PopupRoute<T> {
     this.barrierLabel = 'Dismiss',
     this.barrierColor = kCupertinoModalBarrierColor,
     bool barrierDismissible = true,
-    bool? semanticsDismissible,
+    bool semanticsDismissible = false,
     super.filter,
     super.settings,
     this.anchorPoint,
-  }) {
-    _barrierDismissible = barrierDismissible;
+  }) : _barrierDismissible = barrierDismissible,
        _semanticsDismissible = semanticsDismissible;
-  }
 
   /// A builder that builds the widget tree for the [CupertinoModalPopupRoute].
   ///
@@ -1029,9 +1027,9 @@ class CupertinoModalPopupRoute<T> extends PopupRoute<T> {
   /// widget needs to update dynamically.
   final WidgetBuilder builder;
 
-  bool? _barrierDismissible;
+  final bool _barrierDismissible;
 
-  bool? _semanticsDismissible;
+  final bool _semanticsDismissible;
 
   @override
   final String barrierLabel;
@@ -1040,10 +1038,10 @@ class CupertinoModalPopupRoute<T> extends PopupRoute<T> {
   final Color? barrierColor;
 
   @override
-  bool get barrierDismissible => _barrierDismissible ?? true;
+  bool get barrierDismissible => _barrierDismissible;
 
   @override
-  bool get semanticsDismissible => _semanticsDismissible ?? false;
+  bool get semanticsDismissible => _semanticsDismissible;
 
   @override
   Duration get transitionDuration => _kModalPopupTransitionDuration;
@@ -1167,7 +1165,7 @@ Future<T?> showCupertinoModalPopup<T>({
   Color barrierColor = kCupertinoModalBarrierColor,
   bool barrierDismissible = true,
   bool useRootNavigator = true,
-  bool? semanticsDismissible,
+  bool semanticsDismissible = false,
   RouteSettings? routeSettings,
   Offset? anchorPoint,
 }) {

packages/flutter/lib/src/cupertino/tab_view.dart

@@ -175,13 +175,13 @@ class _CupertinoTabViewState extends State<CupertinoTabView> {
 
   Route<dynamic>? _onGenerateRoute(RouteSettings settings) {
     final String? name = settings.name;
-    WidgetBuilder? routeBuilder;
+    final WidgetBuilder? routeBuilder;
     String? title;
     if (name == Navigator.defaultRouteName && widget.builder != null) {
       routeBuilder = widget.builder;
       title = widget.defaultTitle;
-    } else if (widget.routes != null) {
-      routeBuilder = widget.routes![name];
+    } else {
+      routeBuilder = widget.routes?[name];
     }
     if (routeBuilder != null) {
       return CupertinoPageRoute<dynamic>(
@@ -190,10 +190,7 @@ class _CupertinoTabViewState extends State<CupertinoTabView> {
         settings: settings,
       );
     }
-    if (widget.onGenerateRoute != null) {
-      return widget.onGenerateRoute!(settings);
-    }
-    return null;
+    return widget.onGenerateRoute?.call(settings);
   }
 
   Route<dynamic>? _onUnknownRoute(RouteSettings settings) {