settings: use requireData for AsyncSnapshots

packages/settings/lib/src/widgets/checkbox_settings_tile.dart

@@ -18,7 +18,7 @@ class CheckBoxSettingsTile extends InputSettingsTile<ToggleOption> {
                     : CheckboxListTile(
                         title: Text(option.label(context)),
                         value: value,
-                        onChanged: enabledSnapshot.data!
+                        onChanged: enabledSnapshot.requireData
                             ? (final value) async {
                                 await option.set(value!);
                               }

packages/settings/lib/src/widgets/dropdown_button_settings_tile.dart

@@ -42,12 +42,12 @@ class DropdownButtonSettingsTile<T> extends InputSettingsTile<SelectOption<T>> {
                           child: DropdownButton<T>(
                             isExpanded: true,
                             value: value,
-                            items: valuesSnapshot.data!.keys
+                            items: valuesSnapshot.requireData.keys
                                 .map(
                                   (final k) => DropdownMenuItem(
                                     value: k,
                                     child: Text(
-                                      valuesSnapshot.data![k]!(context),
+                                      valuesSnapshot.requireData[k]!(context),
                                       overflow: TextOverflow.ellipsis,
                                     ),
                                   ),