OSV-2020-852 Use-of-uninitialized-value in H5MM_xstrdup

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=21457 Crash type: Use-of-uninitialized-value Crash state: H5MMxstrdup H5Epushstack H5Eprintfstack...