Fix #30 - cope with missing flight durations
Fix #30 - cope with missing flight durations

SecureCloud-biz/droneshare,diydrones/droneshare,diydrones/droneshare,SecureCloud-biz/droneshare,dronekit/droneshare,dronekit/droneshare,PHELiOX/droneshare,PHELiOX/droneshare,diydrones/droneshare,PHELiOX/droneshare,SecureCloud-biz/droneshare,dronekit/droneshare