Bugfix: "Error obtaining intersections" in navigation.cc

[sadanand1120]

Lets say you set a navigation goal through robofleet. Once the goal is reached you teleop the robot away from that goal. As soon as it tries to get out of the carrot circle centered at the previous nav goal, "Error obtaining intersections" starts getting outputted to stdout. So desired behavior is that once the nav target is reached, you should not see this error popping on the screen when you try to teleop the robot to a different location.