[NNBD] Migrate sample code (#72938)

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

@@ -3014,7 +3014,7 @@ class InputDecoration {
   /// If null, a [BoxConstraints] with a minimum width and height of 48px is
   /// used.
   ///
-  /// {@tool dartpad --template=stateless_widget_scaffold_no_null_safety}
+  /// {@tool dartpad --template=stateless_widget_scaffold}
   /// This example shows the differences between two `TextField` widgets when
   /// [suffixIconConstraints] is set to the default value and when one is not.
   ///

packages/flutter/lib/src/widgets/nested_scroll_view.dart

@@ -58,7 +58,7 @@ typedef NestedScrollViewHeaderSliversBuilder = List<Widget> Function(BuildContex
 /// (those inside the [TabBarView], hooking them together so that they appear,
 /// to the user, as one coherent scroll view.
 ///
-/// {@tool sample --template=stateless_widget_material_no_null_safety}
+/// {@tool sample --template=stateless_widget_material}
 ///
 /// This example shows a [NestedScrollView] whose header is the combination of a
 /// [TabBar] in a [SliverAppBar] and whose body is a [TabBarView]. It uses a
@@ -220,7 +220,7 @@ typedef NestedScrollViewHeaderSliversBuilder = List<Widget> Function(BuildContex
 /// configuration, the flexible space of the app bar will open and collapse,
 /// while the primary portion of the app bar remains pinned.
 ///
-/// {@tool sample --template=stateless_widget_material_no_null_safety}
+/// {@tool sample --template=stateless_widget_material}
 ///
 /// This simple example shows a [NestedScrollView] whose header contains a
 /// floating [SliverAppBar]. By using the [floatHeaderSlivers] property, the
@@ -281,7 +281,7 @@ typedef NestedScrollViewHeaderSliversBuilder = List<Widget> Function(BuildContex
 /// for the nested "inner" scroll view below to end up under the [SliverAppBar]
 /// even when the inner scroll view thinks it has not been scrolled.
 ///
-/// {@tool sample --template=stateless_widget_material_no_null_safety}
+/// {@tool sample --template=stateless_widget_material}
 ///
 /// This simple example shows a [NestedScrollView] whose header contains a
 /// snapping, floating [SliverAppBar]. _Without_ setting any additional flags,
@@ -500,7 +500,7 @@ class NestedScrollView extends StatefulWidget {
 /// [NestedScrollView], you can get its [NestedScrollViewState] by supplying a
 /// `GlobalKey<NestedScrollViewState>` to the [NestedScrollView.key] parameter).
 ///
-/// {@tool dartpad --template=stateless_widget_material_no_null_safety}
+/// {@tool dartpad --template=stateless_widget_material}
 /// [NestedScrollViewState] can be obtained using a [GlobalKey].
 /// Using the following setup, you can access the inner scroll controller
 /// using `globalKey.currentState.innerController`.
@@ -527,7 +527,7 @@ class NestedScrollView extends StatefulWidget {
 /// }
 ///
 /// ScrollController get innerController {
-///   return globalKey.currentState.innerController;
+///   return globalKey.currentState!.innerController;
 /// }
 /// ```
 /// {@end-tool}