OSV-2020-319 Use-of-uninitialized-value in inv_txfm2d_add_facade

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12552 Crash type: Use-of-uninitialized-value Crash state: invtxfm2daddfacade av1invtxfm2dadd64x64c av1inversetransformblock...