fix: Use default value for empty env vars

[simster7]

Set but empty env vars should use the default value instead of panic-ing

Signed-off-by: Simon Behar simbeh7@gmail.com

Don't bother creating a PR until you've done this:

• Run make pre-commit -B to fix codegen, lint, and commit message problems.

Create your PR as a draft.

• Your PR needs to pass the required checks before it can be approved. If the check is not required (e.g. E2E tests) it
  does not need to pass.
• Once required tests have passed, you can make it "Ready for review".
• Say how how you tested your changes. If you changed the UI, attach screenshots.

Tips:

• If changes were requested, and you've made them, then dismiss the review to get it looked at again.
• Add you organization to USERS.md if you like.
• You can ask for help!