Vision sensor issue in VR environment

[sujaygarlanka]

When I put both a Fetch robot and Behavior Robot in a VR environment (Behavior robot is the VR avatar) and have a vision sensor in environment YAML file, I get the issue below. I believe this may be a bug in mesh_renderer_cpu.py where it tries to get RGB data for all robots in the scene and fails when it reaches the Behavior Robot. I think it needs to skip the Behavior Robots. Is this in fact a bug or an issue on my end? Thanks.

Traceback (most recent call last):
  File "main.py", line 79, in <module>
    main()
  File "main.py", line 73, in main
    state, reward, done, _ = env.step(action)
  File "C:\Users\icaro\513-final-project\igibson\envs\igibson_env.py", line 360, in step
    state = self.get_state()
  File "C:\Users\icaro\513-final-project\igibson\envs\igibson_env.py", line 279, in get_state
    vision_obs = self.sensors["vision"].get_obs(self)
  File "C:\Users\icaro\513-final-project\igibson\sensors\vision_sensor.py", line 155, in get_obs
    raw_vision_obs = env.simulator.renderer.render_robot_cameras(modes=self.raw_modalities)
  File "C:\Users\icaro\513-final-project\igibson\render\mesh_renderer\mesh_renderer_cpu.py", line 1256, in render_robot_cameras
    frames.extend(self.render_single_robot_camera(robot, modes=modes, cache=cache))
  File "C:\Users\icaro\513-final-project\igibson\render\mesh_renderer\mesh_renderer_cpu.py", line 1270, in render_single_robot_camera
    for item in self.render(modes=modes, hidden=hide_instances):
TypeError: 'NoneType' object is not iterable