Problems in Flutter tutorial "Write your first Flutter app on the web."

I’ve started learning Flutter. I’m on Write your first Flutter app on the web. I’m doing the web app, not the Android app.

Is this forum the best place to report problems with the tutorial? Or is there a Git repository where I should make a pull request?

The code runs in the DartPad. In Android Studio the code crashes. The error is:

LateInitializationError: Field '_colorAnimation' has not been initialized.

Then it says Bottom Overflowed by 99516 Pixels.

_colorAnimation is called at the end of the program in this widget:

  Widget build(BuildContext context) {
    return AnimatedBuilder(
        animation: _controller,
        builder: (context, child) => LinearProgressIndicator(
      value: _curveAnimation.value,
      valueColor: _colorAnimation,
      backgroundColor: _colorAnimation.value?.withOpacity(0.4),

Why does the code run in DartPad but not in Android Studio? Do I need to worry about this or should I forget it and move on to the next lesson?

I also ran into a problem in section Step 2.5: Launch Dart DevTools. I launched Flutter DevTools and got the screen shown in step 5, but then in the section “Set a Breakpoint” I ran into problems. This section has some formatting problems. The section numbering resets from 5 to 1. Then there are two sections titled “Set a Break Point.” The first of these sections should be titled “Select a Library.”

And that’s where I got stuck. When I switch from Flutter Inspector to Debugger I see Call stack, Variables, and Breakpoints but I don’t see Libraries. Because I can’t select a library I can’t get any code to show in the debugger.