fix  #1089 : voting parallel bug for sparse data
fix  #1089 : voting parallel bug for sparse data

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