Null pointer fix to case when tracker is not found in database. Improved logging.
Null pointer fix to case when tracker is not found in database. Improved logging.

RuuviTracker/ruuvitracker_server,sushilhalai/GPS,ruuvi/ruuvitracker_server,jsyrjala/ruuvitracker_server,ruuvi/ruuvitracker_server,RuuviTracker/ruuvitracker_server,jsyrjala/ruuvitracker_server,ruuvi/ruuvitracker_server,RuuviTracker/ruuvitracker_server,sushilhalai/GPS