Fix WebP progressive decoding may do extra calculate because that libwebp will output last_y to zero, which means current image data is not enough to decode first stride
Fix WebP progressive decoding may do extra calculate because that libwebp will output last_y to zero, which means current image data is not enough to decode first stride

altrooz/SDWebImage,tualatrix/SDWebImage,dpettigrew/SDWebImage,awkward/SDWebImage,Insfgg99x/SDWebImage,iheartradio/SDWebImage,rs/SDWebImage,dreampiggy/SDWebImage,dreampiggy/SDWebImage,awkward/SDWebImage,smule/SDWebImage,awkward/SDWebImage,zhang-yawei/SDWebImage,dreampiggy/SDWebImage