a10164b932
FIT files from older devices (and GPX/TCX files) often omit the speed field. The sliding-window best-effort algorithm was treating all such points as speed=0, so no records were ever produced for these activities. Fix: when p.speed_kmh is None but consecutive lat/lon are available, compute haversine segment speed and spread it evenly across the 1Hz interval slots. This mirrors what _gps_stats already does for avg/max speed computation.