fix empty stream http status code

[amirRamirfatahi]

Fixes #254

Pre-submission Checklist

For tests to work you need a working neo4j and redis instance with the example dataset in docker/db-graph

• Testing: Implement and pass new tests for the new features/fixes, cargo test.
• Performance: Ensure new code has relevant performance benchmarks, cargo bench

[SHAcollision]

Looks good! Ready to merge. @amirRamirfatahi remember to "squash and merge"