[fix] Fix IsZero in tree.h (#2932)
[fix] Fix IsZero in tree.h (#2932)

Co-authored-by: Alberto Ferreira <b8b6b62c40943b6e6a98db5305d16eeda351d4a9@feedzai.com>
microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM