fix a warning
fix a warning

Laurae2/LightGBM,henry0312/LightGBM,henry0312/LightGBM,Laurae2/LightGBM,henry0312/LightGBM,microsoft/LightGBM,Laurae2/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,Laurae2/LightGBM,Laurae2/LightGBM,henry0312/LightGBM,microsoft/LightGBM