Merge branch 'spm/229-tree_obs_iterable_error' into 'master'

Check for existence of position when preparing the lookup tables in treeobs

See merge request flatland/flatland!226

flatland/envs/observations.py

@@ -174,13 +174,15 @@ class TreeObsForRailEnv(ObservationBuilder):
         self.location_has_agent_ready_to_depart = {}
 
         for _agent in self.env.agents:
-            if _agent.status in [RailAgentStatus.ACTIVE, RailAgentStatus.DONE]:
+            if _agent.status in [RailAgentStatus.ACTIVE, RailAgentStatus.DONE] and \
+                    _agent.position:
                 self.location_has_agent[tuple(_agent.position)] = 1
                 self.location_has_agent_direction[tuple(_agent.position)] = _agent.direction
                 self.location_has_agent_speed[tuple(_agent.position)] = _agent.speed_data['speed']
                 self.location_has_agent_malfunction[tuple(_agent.position)] = _agent.malfunction_data['malfunction']
 
-            if _agent.status in [RailAgentStatus.READY_TO_DEPART]:
+            if _agent.status in [RailAgentStatus.READY_TO_DEPART] and \
+                    _agent.initial_position:
                 self.location_has_agent_ready_to_depart[tuple(_agent.initial_position)] = \
                     self.location_has_agent_ready_to_depart.get(tuple(_agent.initial_position), 0) + 1