OSV-2020-1176 Use-of-uninitialized-value in put4bitbwtile

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=21434 Crash type: Use-of-uninitialized-value Crash state: put4bitbwtile gtStripContig TIFFRGBAImageGet...