fix(ontology): guard against empty query string in SPARQL generator

[SAY-5]

Closes #870.

_generate_with_llm in trustgraph-flow/trustgraph/query/ontology/sparql_generator.py did:

query = response.get('query', '').strip()
if query.upper().startswith(('SELECT', 'ASK', 'CONSTRUCT', 'DESCRIBE')):
    return SPARQLQuery(
        ...
        query_type=query.split()[0].upper(),
        ...
    )

If the startswith guard is ever weakened during refactoring (the issue's primary concern) and the LLM returns an empty / whitespace-only query, query.split()[0] raises IndexError. The fix computes parts = query.split() once, returns None if empty, and reuses parts[0] for the query_type read.

Tests

tests/unit/test_query/test_sparql_generator.py adds three async cases:

Test	Covers
test_valid_select_response_returns_query	Sanity: well-formed response still yields a SPARQLQuery with query_type='SELECT'.
test_empty_query_does_not_raise_index_error	Empty query field returns None instead of crashing.
test_whitespace_only_query_does_not_raise_index_error	Whitespace-only query returns None after .strip().

The suite uses pytest.importorskip on trustgraph.query.ontology.sparql_generator so it skips cleanly in environments where the package's existing import chain cannot resolve.

Verification

• python -m py_compile on both edited files: clean.
• pytest tests/unit/test_query locally: 340 passed, 3 skipped (the new tests, due to a pre-existing relative-import issue in query_service.py outside the deployed FlowProcessor environment).

[github-actions]

Contributor License Agreement ❌

This PR contains commits from author(s) with no linked GitHub account. All commits must be authored by a GitHub user so the CLA can be verified.

Please ensure the git author email is associated with a GitHub account, or rewrite the commits with a linked identity.

[cybermaggedon]

Hey @SAY-5 this tripped over the CLA check. The email used in git commits isn't linked to a Github account. Once that's fixed you'll be prompted to send a message here which would indicate acceptance of the CLA.

[cybermaggedon]

Other than that, great change, thanks

[SAY-5]

Thanks @cybermaggedon - I'll fix the commit author email and re-push so the CLA check passes.

[cybermaggedon]

Closed as not able to complete the CLA currently. Thanks for your interest in the project!