TextField in a ListView becomes unresponsive

[justinmc]

Partial fix for #102084, along with #123055.

An error (Null check operator) was being swallowed related to that setup of a TapAndDragGestureRecognizer nested in another GestureDetector. This app can reproduce it:

import 'package:flutter/material.dart';

final buggyTextEditingController = TextEditingController(text: 'Keep scrolling while I have an active cursor.');
int activePointers = 0;
void main() {
  runApp(
    MaterialApp(
      home: Scaffold(
        body: Center(
          child: RawGestureDetector(
            gestures: {
              TapAndDragGestureRecognizer: GestureRecognizerFactoryWithHandlers<TapAndDragGestureRecognizer>(
                () => TapAndDragGestureRecognizer(),
                (TapAndDragGestureRecognizer instance) {
                  instance.onTapDown = (TapDragDownDetails? details) {
                    print('justin onTapDown in app');
                  };
                },
              ),
            },
            child: Container(
              width: 200.0,
              height: 100.0,
              color: Colors.red,
            ),
          ),
        ),
      ),
    ),
  );
}

Drag the red box horizontally, then try tapping it. An error is logged.

This PR fixes the error.

The other PR #123055 fixes some state getting mixed up between the drag and the tap that prevented the tap from being accepted.

[Renzo-Olivares]

LGTM