feat: update route_53 validation statements to permit default value

[wadesdev]

When route53_config is set to null (the default), the validation tried to access properties of a null value, causing an error.

The changes fix the issue by adding a null check before trying to access properties of route53_config. Now when route53_config is null (which is the default), the validation will pass instead of throwing an error.

[jjdaurora]

@wadesdev These changes look good to me. I would feel more comfortable with @RobertKeyser or @tvandort reviewing them first.

[RobertKeyser]

Looks good, but two things:

• Bump the version here by a minor version, that'll kick off a release: https://github.com/ethyca/fides-terraform/blob/main/fides-aws-ecs/version.json
• Add a Changelog entry: https://github.com/ethyca/fides-terraform/blob/main/CHANGELOG.md