Change buildscript to only write version if it should be set

[JohannesDeml]

When versioning: None is set the version values should not be overwritten with "none", but kept as is, since that matches the documentation

Changes

• Set the buildVersion and and bundleVersionCode only if the value makes sense

Checklist

• [x] Read the contribution guide and accept the code of conduct
• [x] Readme (updated or not needed)
• [x] Tests (added, updated or not needed)

[github-actions[bot]]