Add a proper default value (instead of simply "0")

src/Vehicle/Vehicle.cc

@@ -398,6 +398,8 @@ void Vehicle::_commonInit(void)
     _addFact(&_flightDistanceFact,      _flightDistanceFactName);
     _addFact(&_flightTimeFact,          _flightTimeFactName);
     _addFact(&_distanceToHomeFact,      _distanceToHomeFactName);
+
+    _hobbsFact.setRawValue(QVariant(QString("0000:00:00")));
     _addFact(&_hobbsFact,               _hobbsFactName);
 
     _addFactGroup(&_gpsFactGroup,       _gpsFactGroupName);