Working towards turning on all lints from package:pedantic. This change includes
the lints that needed cleanup and don't change any behavior.
Applied cleanup:
* Don't explicitly initialize variables to null.
* DO use curly braces for all flow control structures.
* Use `.isEmpty` instead of `.length == 0`.
* Use `.isNotEmpty` instead of `.length > 0` or `! .isEmpty`.
* Use `=` to separate a named parameter from its default value.
The remaining lints from package:pedantic will require cleanup that is less
automatic and will be addressed in later changes.
Change-Id: Ie4c3ba685f8a559209dd14ac037203ecd16252c7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/103086
Reviewed-by: Nate Bosch <nbosch@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>
Nicholas Shahan
2fd1021326