Deconstructor SIGTERM if no camera connected

[Beck-Sisyphus]

Dear Orbbec developers,

Found deconstructor error when launch astra.launch without a camera connected.

^C[camera_base_link3-15] killing on exit [camera_base_link2-14] killing on exit [camera_base_link-12] killing on exit [camera_base_link1-13] killing on exit [camera/depth_registered_metric-11] killing on exit [camera/depth_registered_hw_metric_rect-10] killing on exit [camera/points_xyzrgb_hw_registered-9] killing on exit [camera/depth_points-7] killing on exit [camera/depth_metric-6] killing on exit [camera/depth_registered_rectify_depth-8] killing on exit [camera/depth_metric_rect-5] killing on exit [camera/rgb_rectify_color-3] killing on exit [camera/depth_rectify_depth-4] killing on exit [camera/driver-2] killing on exit [camera/camera_nodelet_manager-1] killing on exit [camera/depth_metric-6] escalating to SIGTERM [camera/depth_points-7] escalating to SIGTERM [camera/depth_metric_rect-5] escalating to SIGTERM [camera/camera_nodelet_manager-1] escalating to SIGTERM shutting down processing monitor... ... shutting down processing monitor complete done