Don't fire the `available-versions` request when `dbRegion` is falsy
(undefined or empty string). Fixes race condition where the request
fires before a region is selected.
## To test
- Confirm no invalid `available-versions` request in the network tab
- Confirm create new project still works
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **Bug Fixes**
* Improved database region validation during project creation to
consistently handle empty or undefined values.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Co-authored-by: Alaister Young <10985857+alaister@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
