OSV-2020-1475 Use-of-uninitialized-value in LibRaw::open_datastream

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=21537 Crash type: Use-of-uninitialized-value Crash state: LibRaw::opendatastream LibRaw::openfile librawopenfile...