ICD11: gracefully return None if issues with redis

[rithviknishad]

Proposed Changes

• ICD11: gracefully return None if issues with redis

Associated Issue

• Front-end: Show ICD-11 Diagnosis functionality unavailable error if issues with Redis care_fe#7973

Merge Checklist

• Tests added/fixed
• Update docs in /docs
• Linting Complete
• Any other necessary step

Only PR's with test cases included and passing lint and test pipelines will be reviewed

@coronasafe/care-backend-maintainers @coronasafe/care-backend-admins

[nihal467]

LGTM tested through tunnel

[vigneshhari]

Keep in mind that this is not just redis exceptions, this is gracefully returning on all exceptions, maybe create a ticket to handle it better in the future.