Make CupertinoThemeData properties non-nullable (#66274)

packages/flutter/lib/src/material/theme_data.dart

@@ -271,7 +271,7 @@ class ThemeData with Diagnosticable {
     FloatingActionButtonThemeData floatingActionButtonTheme,
     NavigationRailThemeData navigationRailTheme,
     Typography typography,
-    CupertinoThemeData cupertinoOverrideTheme,
+    NoDefaultCupertinoThemeData cupertinoOverrideTheme,
     SnackBarThemeData snackBarTheme,
     BottomSheetThemeData bottomSheetTheme,
     PopupMenuThemeData popupMenuTheme,
@@ -1080,7 +1080,7 @@ class ThemeData with Diagnosticable {
   ///
   /// This cascading effect for individual attributes of the [CupertinoThemeData]
   /// can be overridden using attributes of this [cupertinoOverrideTheme].
-  final CupertinoThemeData cupertinoOverrideTheme;
+  final NoDefaultCupertinoThemeData cupertinoOverrideTheme;
 
   /// A theme for customizing the color, elevation, and shape of a bottom sheet.
   final BottomSheetThemeData bottomSheetTheme;
@@ -1211,7 +1211,7 @@ class ThemeData with Diagnosticable {
     FloatingActionButtonThemeData floatingActionButtonTheme,
     NavigationRailThemeData navigationRailTheme,
     Typography typography,
-    CupertinoThemeData cupertinoOverrideTheme,
+    NoDefaultCupertinoThemeData cupertinoOverrideTheme,
     SnackBarThemeData snackBarTheme,
     BottomSheetThemeData bottomSheetTheme,
     PopupMenuThemeData popupMenuTheme,
@@ -1682,7 +1682,7 @@ class ThemeData with Diagnosticable {
     properties.add(DiagnosticsProperty<FloatingActionButtonThemeData>('floatingActionButtonThemeData', floatingActionButtonTheme, defaultValue: defaultData.floatingActionButtonTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<NavigationRailThemeData>('navigationRailThemeData', navigationRailTheme, defaultValue: defaultData.navigationRailTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<Typography>('typography', typography, defaultValue: defaultData.typography, level: DiagnosticLevel.debug));
-    properties.add(DiagnosticsProperty<CupertinoThemeData>('cupertinoOverrideTheme', cupertinoOverrideTheme, defaultValue: defaultData.cupertinoOverrideTheme, level: DiagnosticLevel.debug));
+    properties.add(DiagnosticsProperty<NoDefaultCupertinoThemeData>('cupertinoOverrideTheme', cupertinoOverrideTheme, defaultValue: defaultData.cupertinoOverrideTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<SnackBarThemeData>('snackBarTheme', snackBarTheme, defaultValue: defaultData.snackBarTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<BottomSheetThemeData>('bottomSheetTheme', bottomSheetTheme, defaultValue: defaultData.bottomSheetTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<PopupMenuThemeData>('popupMenuTheme', popupMenuTheme, defaultValue: defaultData.popupMenuTheme, level: DiagnosticLevel.debug));
@@ -1759,7 +1759,7 @@ class MaterialBasedCupertinoThemeData extends CupertinoThemeData {
       );
 
   final ThemeData _materialTheme;
-  final CupertinoThemeData _cupertinoOverrideTheme;
+  final NoDefaultCupertinoThemeData _cupertinoOverrideTheme;
 
   @override
   Brightness get brightness => _cupertinoOverrideTheme.brightness ?? _materialTheme.brightness;