Target of URI doesn't exist - how to fix?

// Automatic FlutterFlow imports
import '/backend/schema/structs/index.dart';
import '/backend/schema/enums/enums.dart';
import '/flutter_flow/flutter_flow_theme.dart';
import '/flutter_flow/flutter_flow_util.dart';
import '/custom_code/widgets/index.dart'; // Imports other custom widgets
import '/custom_code/actions/index.dart'; // Imports custom actions
import '/flutter_flow/custom_functions.dart'; // Imports custom functions
import 'package:flutter/material.dart';
// Begin custom widget code
// DO NOT REMOVE OR MODIFY THE CODE ABOVE!

import 'package:flutter_colorpicker/flutter_colorpicker.dart';
import './pickers/hsv_picker.dart';
import './pickers/material_picker.dart';
import './pickers/block_picker.dart';

class ColorPickr extends StatefulWidget {
  const ColorPickr({
    super.key,
    this.width,
    this.height,
    required this.pickerColor,
    required this.currentColor,
    required this.changeColor,
  });

  final double? width;
  final double? height;
  final Color pickerColor;
  final Color currentColor;
  final Future Function(Color color) changeColor;

  @override
  State<ColorPickr> createState() => _ColorPickrState();
}

class _ColorPickrState extends State<ColorPickr> {
  @override
  Widget build(BuildContext context) {
    final foregroundColor =
        useWhiteForeground(currentColor) ? Colors.white : Colors.black;
    return AnimatedTheme(
      data: lightTheme ? ThemeData.light() : ThemeData.dark(),
      child: Builder(builder: (context) {
        return DefaultTabController(
          length: 3,
          child: Scaffold(
            floatingActionButton: FloatingActionButton.extended(
              onPressed: () => setState(() => lightTheme = !lightTheme),
              icon: Icon(lightTheme
                  ? Icons.dark_mode_rounded
                  : Icons.light_mode_rounded),
              label: Text(lightTheme ? 'Night' : '  Day '),
              backgroundColor: currentColor,
              foregroundColor: foregroundColor,
              elevation: 15,
            ),
            appBar: AppBar(
              title: const Text('Flutter Color Picker Example'),
              backgroundColor: currentColor,
              foregroundColor: foregroundColor,
              bottom: TabBar(
                labelColor: foregroundColor,
                tabs: const <Widget>[
                  Tab(text: 'HSV/HSL/RGB'),
                  Tab(text: 'Material'),
                  Tab(text: 'Blocky'),
                ],
              ),
            ),
            body: TabBarView(
              children: <Widget>[
                HSVColorPickerExample(
                  pickerColor: currentColor,
                  onColorChanged: changeColor,
                  colorHistory: colorHistory,
                  onHistoryChanged: (List<Color> colors) =>
                      colorHistory = colors,
                ),
                MaterialColorPickerExample(
                    pickerColor: currentColor, onColorChanged: changeColor),
                BlockColorPickerExample(
                  pickerColor: currentColor,
                  onColorChanged: changeColor,
                  pickerColors: currentColors,
                  onColorsChanged: changeColors,
                  colorHistory: colorHistory,
                ),
              ],
            ),
          ),
        );
      }),
    );
  }
}