fix: actually throw error in environmentExists if the environment doesn't exist

[shreddedbacon]

General Checklist

• [ ] Affected Issues have been mentioned in the Closing issues section
• [ ] Documentation has been written/updated
• [ ] PR title is ready for inclusion in changelog

Database Migrations

• [ ] If your PR contains a database migation, it MUST be the latest in date order alphabetically

Fix the environment exists validator check to actually throw the error if the environment doesn't exist.