OSV-2020-1784 Use-of-uninitialized-value in put_unweighted_pred_16_fallback

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=25707 Crash type: Use-of-uninitialized-value Crash state: putunweightedpred16fallback accelerationfunctions::putunweightedpred generateinterpredictionsamples...