OSV-2017-67 Heap-buffer-overflow in OSS_FUZZ_png_combine_row

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=3608 Crash type: Heap-buffer-overflow WRITE Crash state: OSSFUZZpngcombinerow OSSFUZZpngreadrow start...