avoid NaN output.
avoid NaN output.

huanzhang12/LightGBM,huanzhang12/lightgbm-gpu,huanzhang12/lightgbm-gpu,huanzhang12/LightGBM,huanzhang12/lightgbm-gpu,huanzhang12/lightgbm-gpu,huanzhang12/LightGBM,huanzhang12/lightgbm-gpu,huanzhang12/LightGBM,huanzhang12/LightGBM