### What problem does this PR solve?
When using the 'metadata_condition' for metadata filtering, if no
documents match the filtering criteria, the system will return the
search results of all documents instead of returning an empty result.
When the metadata_condition has conditions but no matching documents,
simply return an empty result.
#11572
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
Co-authored-by: Chenguang Wang <chenguangwang@deepglint.com>
918d5a9ff8