Bug in VehiclePosition::updateRelativePosition(), unexistant index

Problem seems to appear after adding a new service from synthese/ops

Important: Please do not "solve" this problem by replacing at(x) with operator[]

DB: tpc_preprod

WARN  # 2018/10/30 10:07:29.377609000 # Job processor # Missing metric offset for edge rank=6 in path id=2533493833728226, calculated value is 0
ERROR # 2018/10/30 10:07:29.377757000 # Job processor # VehiclePosition 20266451726237701: updateRelativePosition() std exeption caught : Unable to find key in unordered_map.
DEBUG # 2018/10/30 10:07:30.402837000 # HTTP_1 # 217.79.206.25 # Received request : /vehicle_tracking/update_gps?longitude=6.6324913&serviceId=4503818670704031&sid=mobichablais&latitude=46.5163667 (112 bytes)

About first log line Missing metric offset (...) please see issue #860 (closed)