Fix AttributeError when tool fields are None in OpenAI Agents SDK instrumentation (#1285)

[YouFoxGirl]

Summary

In get_response_tool_web_search_attributes() and get_response_tool_file_search_attributes(), hasattr() returns True for optional fields set to None, but accessing .__dict__ on None raises AttributeError.

Fix

Added is not None guard for user_location, filters, and ranking_options fields in agentops/instrumentation/providers/openai/attributes/response.py:

# Before (buggy)
if hasattr(tool, "user_location"):
    parameters["user_location"] = tool.user_location.__dict__

# After (fixed)
if hasattr(tool, "user_location") and tool.user_location is not None:
    parameters["user_location"] = tool.user_location.__dict__

Same pattern applied to filters and ranking_options.

Testing

Added regression tests in tests/unit/instrumentation/providers/openai/test_response_issue_1285.py covering all three None-field cases. All 5 tests pass.

Fixes #1285