Fix an issue where the diff wouldn't render and improve logic

opentech/apply/funds/differ.py

...pply/funds/templates/funds/includes/rendered_answers.html

opentech/apply/funds/templates/funds/revisions_compare.html

opentech/apply/funds/tests/factories/blocks.py

opentech/apply/funds/tests/test_views.py

opentech/apply/funds/views.py