fix(api/configs): Ignore empty environment variables when loading config.

[laipz8200]

Description

Ensure that default values in the configuration items are correctly loaded by ignoring potential null values in the environment variables.

Ref

Fixes #5640 (issue)

Type of Change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Suggested Checklist:

• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] My changes generate no new warnings
• [x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods
• [ ] optional I have made corresponding changes to the documentation
• [ ] optional I have added tests that prove my fix is effective or that my feature works
• [ ] optional New and existing unit tests pass locally with my changes

[laipz8200]

cc @bowenliang123

[bowenliang123]

Thanks!