### What problem does this PR solve?

This pull request addresses an issue where the reference is an empty
array ([]) in specific cases, leading to errors in the application. When
the reference is empty, the code attempts to call the get method on a
list, resulting in the following error message:
``` json
{"retcode": 500, "retmsg": "'list' object has no attribute 'get'", "data": {"answer": "**ERROR**: 'list' object has no attribute 'get'", "reference": []}}
```

### Type of change

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

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>