I use my own model resulted in backbones generating 0 candidate boxes, which resulting in errors in the postprocess module

[ACFIRSTONE]

I have improved the pillars based model and will use this project for tensorrt acceleration. As only vehicles will be detected, objects cannot be detected in some scenes, so the backbone network will generate 0 candidates, which will cause the postprocess module to report an error. I added the judgment for bndbox_num in lidar-postprocess.cu before line 472 (because there is an error), and if it is 0, return, which avoids the error if (bndbox_num==0) return;