Update Habitat-API to allow for no rendering sensors (#139)

Update Habitat-API to allow for no rendering sensors

habitat/sims/habitat_simulator/habitat_simulator.py

@@ -189,13 +189,6 @@ class HabitatSim(Simulator):
             sim_sensor_cfg.sensor_type = sensor.sim_sensor_type  # type: ignore
             sensor_specifications.append(sim_sensor_cfg)
 
-        # If there is no sensors specified create a dummy sensor so simulator
-        # won't throw an error
-        if not _sensor_suite.sensors.values():
-            sim_sensor_cfg = habitat_sim.SensorSpec()
-            sim_sensor_cfg.resolution = [1, 1]
-            sensor_specifications.append(sim_sensor_cfg)
-
         agent_config.sensor_specifications = sensor_specifications
         agent_config.action_space = registry.get_action_space_configuration(
             self.config.ACTION_SPACE_CONFIG