Redirects from '/' not working

Right now redirects from '/' are not working unless regex is enabled. This bug goes back to untrailingslashit. We need to check for an empty path after removing the trailing slash from requested path like we do with redirect_from. If we have an empty path, we need to change it to '/'.

Tests in the feature/tests branch demonstrate this bug: https://github.com/tlovett1/Safe-Redirect-Manager/tree/bugfix/root-redirect-miss