velociraptor: get_client_flow_results raises IndexError for multi-source artifacts #458

Problem

get_client_flow_results raises IndexError: list index out of range for any artifact that has more
than one source, for example Generic.Client.Info (BasicInformation, DetailedInfo,
LinuxInfo).

query = "SELECT * FROM flow_results(flow_id='" + flow_id + "', client_id='" + client_id + "')"
results = self.request(api_config, query)
return results[0]

Without an artifact= argument, flow_results() returns no rows for a multi-source artifact, so
results[0] fails.

Reproduce

1. Collect Generic.Client.Info on a client and wait for the flow to finish.
2. Call get_client_flow_results with that client and flow id. The action fails with IndexError.
3. The same flow returns rows with flow_results(..., artifact='Generic.Client.Info/BasicInformation').

A single-source artifact (e.g. Linux.Sys.Users) works.

Tested with app velociraptor/1.0.0 at b264148 against Velociraptor 0.77.3.

Suggested fix

• Add an optional artifact parameter (artifact or Artifact/Source) and pass it to flow_results().
• Return the full result list, or [], instead of results[0], so an empty result does not raise.

Happy to send a PR if that direction is OK.