allow empty str input in prompt() when confirmation_prompt=True and default=""

[antazoey]

Check to see if the user inputted nothing (empty str) for their first answer and second answer in the prompt() method when confirmation_prompt=True

• fixes Unable to allow empty str in prompt when confirmation_prompt=True #2157

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs.
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.