PageView, inside ListView, inside Column: `Null check operator used on a null value` - flutter

Question

I have a PageView, inside a ListView, inside a Column. It seems necessary because of the layout (top green widget should be scrollable, but bottom widget shouldn't be).
class MyWidget extends StatefulWidget {
Widget createPage(int page, Color color) {
return Container(
color: color,
child: Padding(
padding: EdgeInsets.symmetric(vertical: 200.0),
child: Text("Page: $page. Swipe right to go to next page"),
),
);
}
late final List<Widget> pages = [
createPage(1, Colors.purple),
createPage(2, Colors.red)
];
#override
createState() => _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
late final PageController _pageController;
int page = 0;
#override
initState() {
super.initState();
_pageController = PageController();
}
#override
Widget build(BuildContext context) {
return Column(
children: [
Expanded(
child: ListView(
children: [
Container(
color: Colors.green,
child: const Text("Top of screen, scrollable.")),
// This works
Column(
children: widget.pages,
),
// PageView tries to take the full height. Without Flexible, PageView is unbounded.
// Flexible(
// child: PageView.builder(
// itemCount: widget.pages.length,
// controller: _pageController,
// onPageChanged: (int index) => setState(() => page = index),
// itemBuilder: (context, index) => widget.pages[index],
// ),
// )
],
),
),
Container(
color: Colors.green, child: const Text("Bottom of screen, always")),
],
);
}
}
However, I get various error based on what I try. This is an unhelpful error, since ListView doesn't have a problem when it's children is a Column:
The following _CastError was thrown during performLayout():
Null check operator used on a null value
The relevant error-causing widget was:
ListView ListView:file:///path/to/project/lib/main.dart:63:18
Code
I've created a Dartpad pad to reproduce this. I've commented out the PageView and replaced it with a column so you can see the app. The issue is replacing Column with 2 pages to PageView.
I've tried various things:
Wrapping ListView in things:
SizedBox.expand(child: ListView(...))
Expanded(child: ListView(...)) following this answer
Flexible(child: ListView(...))
ListView.builder(shrinkWrap: true,...),
Changing mainAxisSize of Column