Fix 'fastlane env' not to crash when Xcode Version cannot be obtained

[nafu]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Description

Fix fastlane env not to crash when Xcode Version cannot be obtained

Motivation and Context

If Xcode Version cannot be obtained, fastlane env crashes and the user cannot get any output of fastlane environment.
e.x. #8187 (comment)

[mfurtak]

Thanks for the fix! 🚀