fix -Wmaybe-uninitialized warning (initialize pointers to NULL)
fix -Wmaybe-uninitialized warning (initialize pointers to NULL)

opencv/opencv,apavlenko/opencv,apavlenko/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv,opencv/opencv