Route53 fix_route53_ids handler can result in confusing error

[tim-finnigan]

Describe the bug

The fix_route53_ids handler for Route53 commands could result in the following error:
AttributeError: 'NoneType' object has no attribute 'split'

See #3025 for more context, specifically #3025 (comment):

...When my manage domains operation creates a certificate validation resource record, it stores the associated DNS name and value in a DynamoDB table as a string set. When a request is made to delete the domain, it pulls the certificate validation DNS details from the DynamoDB table. Since the string set data type doesn't preserve the original order (my mistake for using a string set instead of a list), the DNS name and value parameters are coming back in a different order than how I originally inserted them. Thus when the change_resource_record_sets method is called, the name and value parameters are transposed so the method can't find record set that it is being asked to delete.

And therein lies the bug in botocore. I should be getting some sort of "resource record not found" error returned to the invalid request but instead, it returns the very unhelpful 'NoneType' object has no attribute 'split' error. This seems like a logic error to me. The fix_route53_ids method is being called prior to verifying the resource record's existence.