Show lines stopping in the map, bugfixing

Summary:
Download GTFS realtime position updates

Fix NullPointerException, T1142

Fix NullPointerException of the map, T1146

First solution for T1140: showing the lines on the map

Show lines stopping in the bus stop on the map

Reviewers: valerio.bozzolan

Reviewed By: valerio.bozzolan

Subscribers: valerio.bozzolan, Libre BusTO

Tags: Libre BusTO

Differential Revision: https://gitpull.it/D99