OSV-2020-2138 Use-of-uninitialized-value in Mat_VarReadNextInfo5

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27258 Crash type: Use-of-uninitialized-value Crash state: MatVarReadNextInfo5 MatVarReadNextInfo MatGetDir...