OSV-2020-1006 Use-of-uninitialized-value in decimate_dsd_run

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=19928 Crash type: Use-of-uninitialized-value Crash state: decimatedsdrun WavpackUnpackSamples WavpackSeekSample64...