RDS template fails when making DBFamily and/or EngineMajorVersion empty

[danielkza]

The template conditionally does not create the ParameterGroup and OptionGroup based on whether the aforementioned variables are empty, but refers to them anyway and causes errors:

botocore.exceptions.ClientError: An error occurred (ValidationError) when calling the CreateStack operation: Template format error: Unresolved resource dependencies [OptionGroup, ParameterGroup] in the Resources block of the template