Search failed: 'NoneType' object has no attribute 'lower'

[abn]

Describe the bug
Using the search tool fails. Code seems to expect string when None is returned. See logs. Failure happened while performing a research task, and failure seems to be silent. The research task just stops mid-task without errors.

[2026-03-15 16:24:24.912] [INFO] [lib.rs:4190] reuse idle connection for ("https", yandex.com)
[2026-03-15 16:24:24.912] [INFO] [lib.rs:4190] send frame=Headers { stream_id: StreamId(3), flags: (0x5: END_HEADERS | END_STREAM) }
[2026-03-15 16:24:24.929] [INFO] [lib.rs:4190] received frame=Settings { flags: (0x0), header_table_size: 16384, max_concurrent_streams: 128, initial_window_size: 262144, max_frame_size: 16384, max_header_list_size: 524288 }
[2026-03-15 16:24:24.929] [INFO] [lib.rs:4190] send frame=Settings { flags: (0x1: ACK) }
[2026-03-15 16:24:24.929] [INFO] [lib.rs:4190] encoding SETTINGS; len=0, order=SettingsOrder { ids: [HeaderTableSize, EnablePush, MaxConcurrentStreams, InitialWindowSize, MaxFrameSize, MaxHeaderListSize, EnableConnectProtocol, NoRfc7540Priorities] }, header_table_size=None, enable_push=None, initial_window_size=None, max_frame_size=None, max_header_list_size=None
[2026-03-15 16:24:24.929] [INFO] [lib.rs:4190] received frame=WindowUpdate { stream_id: StreamId(0), size_increment: 196609 }
[2026-03-15 16:24:24.929] [INFO] [lib.rs:4190] received frame=Settings { flags: (0x1: ACK) }
[2026-03-15 16:24:24.929] [INFO] [lib.rs:4190] received settings ACK; applying Settings { flags: (0x0), header_table_size: 65536, enable_push: 0, initial_window_size: 6291456, max_header_list_size: 262144 }
[2026-03-15 16:24:24.971] [INFO] [lib.rs:4190] received frame=Headers { stream_id: StreamId(3), flags: (0x4: END_HEADERS) }
[2026-03-15 16:24:24.971] [INFO] [lib.rs:4190] received frame=Data { stream_id: StreamId(3) }
[2026-03-15 16:24:24.971] [INFO] [lib.rs:4190] received frame=Data { stream_id: StreamId(3), flags: (0x1: END_STREAM) }
[2026-03-15 16:24:24.971] [INFO] [lib.rs:4190] inserting secure cookie '_yasc'
[2026-03-15 16:24:24.971] [INFO] [lib.rs:4190] response: https://yandex.com/showcaptcha?cc=1&form-fb-hint=8.148&mt=*** 200
[2026-03-15 16:24:24.973] [ERROR] [lib.rs:4187] Error in engine brave: AttributeError("'NoneType' object has no attribute 'lower'")
[2026-03-15 16:24:24.974] [ERROR] [lib.rs:4187] {"error":"'NoneType' object has no attribute 'lower'","event":"DuckDuckGo search failed","logger":"nowledge_graph_server.mcp.tools.web_search_tools"}
[2026-03-15 16:24:24.974] [INFO] [lib.rs:4190] {"method": "web_search", "app": "ai-now", "response": "{\"status\": \"error\", \"message\": \"Search failed: 'NoneType' object has no attribute 'lower'\", \"results\": []}", "event": "MCP_RESPONSE", "level": "info", "logger": "nowledge_graph_server.mcp.tools.web_search_tools", "timestamp": "2026-03-15T15:24:24.974143Z"}
[2026-03-15 16:24:24.976] [INFO] [lib.rs:4190] Response sent
[2026-03-15 16:24:24.976] [INFO] [lib.rs:4190] Closing SSE writer
[2026-03-15 16:24:24.976] [ERROR] [lib.rs:4187] chunk: b'event: message\r\ndata: {"jsonrpc":"2.0","id":1,"result":{"content":[{"type":"text","text":"{\\"status\\":\\"error\\",\\"message\\":\\"Search failed: \'NoneType\' object has no attribute \'lower\'\\",\\"results\\":[]}"}],"structuredContent":{"status":"error","message":"Search failed: \'NoneType\' object has no attribute \'lower\'","results":[]},"isError":false}}\r\n\r\n'
[2026-03-15 16:24:24.977] [INFO] [lib.rs:4190] Terminating session: None

To Reproduce
Trigger a search in AI Now when doing a research task. Looks like DuckDuckGo search is required to reproduce error. However, request prior to error was to yandex.

Failure seems to be intermittent.

Expected behavior
Search succeeds.