More artifacts at: b/143568219

Crash observed on iOS 12.4.1 and 13.1. Repros with this simple layout:

MaterialApp(
        home: Scaffold(
            body: Center(
                child: Container(
      color: Colors.white,
      child: TextField(),
    ))));

steps:

1. a11y-focus the TextField and double-tap to bring up the keyboard
2. Tap the TextField again to make sure it has the a11y border around it
3. Toggle voiceover off then on again (I'm using the iOS triple-click shortcut) to get a native EXC_BAD_ACCESS in AccessibilityBridge::textInputView.