Flutter : Error - RenderBox was not laid out: RenderPointerListener#f99db relayoutBoundary=up18 NEEDS-PAINT

class Test extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return  MaterialApp(
      
        home: Scaffold(
        appBar: AppBar(
        title:Row( children:<Widget> [  TopbarSearchText()], ),
  
    ) 
    )
    );
  }
}
class TopbarSearchText extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return TextField(

      decoration: const InputDecoration(
          fillColor: Colors.white,filled: true,
          border: OutlineInputBorder(),
          prefixIcon: Icon(Icons.search),

          hintText: 'Enter a search term'),
    );
  }
}

The following assertion was thrown during performLayout():
RenderBox was not laid out: RenderIgnorePointer#abaa5 relayoutBoundary=up16 NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
'package:flutter/src/rendering/box.dart':
Failed assertion:: 'hasSize'


Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.

Expanded(child: TopbarSearchText()) 

class Test extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return  MaterialApp(
      
        home: Scaffold(
        appBar: AppBar(
        title:Row( children:<Widget> [  Expanded(child:TopbarSearchText())], ),
  
    ) 
    )
    );
  }
}
class TopbarSearchText extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return TextField(

      decoration: const InputDecoration(
          fillColor: Colors.white,filled: true,
          border: OutlineInputBorder(),
          prefixIcon: Icon(Icons.search),

          hintText: 'Enter a search term'),
    );
  }
}