Handle null values in ETA and/or boat departure time

[ckulfan]

When the boats get too far off schedule, it appears that the ferry system does not pupulate the ETA and departure time data. This throws off our ETA, departure delay, and average departure delay calculations. See example packet in the comments below. We could compute our own ETA based on boat departure time. Not sure how we would compute the departure delay without knowing the entire schedule.

[ckulfan]

{
"VesselID": 32,
"VesselName": "Tacoma",
"Mmsi": 366772760,
"DepartingTerminalID": 3,
"DepartingTerminalName": "Bainbridge Island",
"DepartingTerminalAbbrev": "BBI",
"ArrivingTerminalID": 7,
"ArrivingTerminalName": "Seattle",
"ArrivingTerminalAbbrev": "P52",
"Latitude": 47.612245,
"Longitude": -122.418902,
"Speed": 18.8,
"Heading": 95,
"InService": true,
"AtDock": false,
"LeftDock": null,
"Eta": null,
"EtaBasis": "Vessel Tacoma departed Bainbridge going to Colman and using vessel Tacoma closest location data from Jun 3 2024 1:55PM",
"ScheduledDeparture": null,
"OpRouteAbbrev": [
"sea-bi"
],
"VesselPositionNum": 1,
"SortSeq": 60,
"ManagedBy": 1,
"TimeStamp": "/Date(1717456456000-0700)/",
"VesselWatchShutID": 20,
"VesselWatchShutMsg": "VesselWatch data temporarily unavailable. ",
"VesselWatchShutFlag": "0",
"VesselWatchStatus": "0",
"VesselWatchMsg": "WSF's VesselWatch page is currently not responding and is out of service. Thank you for your patience while we work to restore this page. "
},
{
"VesselID": 74,
"VesselName": "Chimacum",
"Mmsi": 367712660,
"DepartingTerminalID": 7,
"DepartingTerminalName": "Seattle",
"DepartingTerminalAbbrev": "P52",
"ArrivingTerminalID": 3,
"ArrivingTerminalName": "Bainbridge Island",
"ArrivingTerminalAbbrev": "BBI",
"Latitude": 47.60256,
"Longitude": -122.399263,
"Speed": 15.8,
"Heading": 268,
"InService": true,
"AtDock": false,
"LeftDock": null,
"Eta": null,
"EtaBasis": "Vessel Chimacum departed Colman going to Bainbridge and using vessel Chimacum closest location data from Jun 3 2024 2:13PM",
"ScheduledDeparture": null,
"OpRouteAbbrev": [
"sea-bi"
],
"VesselPositionNum": 2,
"SortSeq": 60,
"ManagedBy": 1,
"TimeStamp": "/Date(1717456456000-0700)/",
"VesselWatchShutID": 11,
"VesselWatchShutMsg": "11;25am SEA delayed due to medical emergency.",
"VesselWatchShutFlag": "0",
"VesselWatchStatus": "0",
"VesselWatchMsg": "WSF's VesselWatch page is currently not responding and is out of service. Thank you for your patience while we work to restore this page. "
},