Fix noisy null-safety warning

[metalbass]

Problem

When importing 'package:noob/noob.dart', with flutter stable v3.0.5, we see a bunch of red warnings in the console about using the null-check operator ! over WidgetsBinding.instance, that is not nullable.

Warnings as seen in console

/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/noob-0.0.7/lib/src/tools/providers.dart:12:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/C:/src/flutter/packages/flutter/lib/src/widgets/binding.dart').
    WidgetsBinding.instance!.pointerRouter.addGlobalRoute(_handler);
                   ^
/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/noob-0.0.7/lib/src/tools/providers.dart:17:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/C:/src/flutter/packages/flutter/lib/src/widgets/binding.dart').
    WidgetsBinding.instance!.pointerRouter.removeGlobalRoute(_handler);
                   ^
/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/noob-0.0.7/lib/src/tools/providers.dart:50:20: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/C:/src/flutter/packages/flutter/lib/src/widgets/binding.dart').
    WidgetsBinding.instance!.addPostFrameCallback(_callback);
                   ^
/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/noob-0.0.7/lib/src/tools/providers.dart:64:22: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/C:/src/flutter/packages/flutter/lib/src/widgets/binding.dart').
      WidgetsBinding.instance!.addPostFrameCallback(_callback);
                     ^
/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/noob-0.0.7/lib/src/build_tracker/build_tracker.dart:123:22: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/C:/src/flutter/packages/flutter/lib/src/widgets/binding.dart').
      WidgetsBinding.instance!.addPostFrameCallback(_frameCallback);
                     ^
/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/noob-0.0.7/lib/src/build_tracker/build_tracker.dart:197:22: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/C:/src/flutter/packages/flutter/lib/src/widgets/binding.dart').
      WidgetsBinding.instance!.addPostFrameCallback(_frameCallback);
                     ^
/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/noob-0.0.7/lib/src/build_tracker/tracking_build_owner.dart:41:27: Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('/C:/src/flutter/packages/flutter/lib/src/widgets/binding.dart').
    return WidgetsBinding.instance!;
                          ^

flutter doctor

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 3.0.5, on Microsoft Windows [Versi¢n 10.0.22000.856], locale es-ES)
[√] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
[√] Chrome - develop for the web
[X] Visual Studio - develop for Windows
    X Visual Studio not installed; this is necessary for Windows development.
      Download at https://visualstudio.microsoft.com/downloads/.
      Please install the "Desktop development with C++" workload, including all of its default components
[√] Android Studio (version 2021.2)
[√] Connected device (3 available)
[√] HTTP Host Availability

! Doctor found issues in 1 category.

Solution

Remove redundant null-check operator ! over WidgetsBinding.instance

Unresolved topics

Compatibility with previous versions

I'm assuming this was working without warnings in previous versions of flutter, where WidgetsBinding was nullable, likely to not supporting null-safety at that time.

We may need to ensure that compatibility between different flutter versions and this package, but since I don't know much about this right now, I didn't resolve this aspect.

TrackingBuildOwnerWidgetsFlutterBinding.ensureInitialized is not working

TrackingBuildOwnerWidgetsFlutterBinding.ensureInitialized is not working, as it's checking if WidgetsBinding.instance is null, which won't happen:

static WidgetsBinding ensureInitialized() {
  if (WidgetsBinding.instance == null) {
    TrackingBuildOwnerWidgetsFlutterBinding();
  }
  return WidgetsBinding.instance;
}

But calling TrackingBuildOwnerWidgetsFlutterBinding(); instead before creating a BuildTracker works fine:

void main() {
  TrackingBuildOwnerWidgetsFlutterBinding();
  BuildTracker();
  runApp(...);
}

There seems to be some changes in recent versions of flutter about how this is handled; and calling TrackingBuildOwnerWidgetsFlutterBinding(); directly sounds like a small hack, but it works for me.

Increase version number and add entry in the changelog

As I don't know if this must be a 0.0.8 or a 1.0.0 (if fixing ensureInitialized ends up in a breaking change), I still haven't added an entry on the changelog.

[derolf]

1000 thanks!