check nullable of bin_mappers in DatasetLoader::CheckCategoricalFeatureNumBin (fix #5145) (#5146)
check nullable of bin_mappers in DatasetLoader::CheckCategoricalFeatureNumBin (fix #5145) (#5146)


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