[BUG] SIGSEGV endpoints with data:// location for some table functions #43
Description
The problem:
When a Flight server returns endpoints with data:// URIs containing encoded DuckDB table function calls (media type application/x-msgpack-duckdb-function-call;base64), the extension creates an AirportLocalScanData to execute the function locally. However, AirportLocalScanData (in src/airport_flight_stream.cpp) assumes the table function follows the standard function pattern - it requires init_global and calls table_function.function() to produce output.
Functions like generate_series and range use the in_out_function pattern instead:
- init_global = nullptr (no global state)
- function = nullptr (the main scan callback)
- in_out_function is set (the actual execution path)
This causes a SIGSEGV at src/airport_flight_stream.cpp:309 when func.init_global(context, input) is called on a null function pointer.
Even if init_global were guarded, AirportDataFromLocalScanFunction at src/airport_take_flight.cpp:371 would also crash calling scan_data->table_function.function(context, function_input, output) on a null pointer.
Temporary fix: throw NotImplementedException when func.init_global is null (airport_flight_stream.cpp:306-307).
Permanent fix: Extend AirportLocalScanData and AirportDataFromLocalScanFunction to support the in_out_function execution pattern - handle null init_global/init_local, and call in_out_function/in_out_function_final instead of function when appropriate.