`Paragraph.getBoxesForPlaceholders` returns NaN when font size is zero. Reference: https://github.com/daohoangson/flutter_widget_from_html/issues/578

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    ));

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final style = DefaultTextStyle.of(context).style;
    return SingleChildScrollView(
      child: RichText(
        text: TextSpan(
          children: [
            const WidgetSpan(child: SizedBox(width: 10, height: 10)),
            TextSpan(text: 'hover me', style: style),
          ],
          style: style.copyWith(fontSize: 0.0),
        ),
      ),
    );
  }
}