OSV-2017-72 Use-of-uninitialized-value in _gnutls_mpi_dprint_size

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=1494 Crash type: Use-of-uninitialized-value Crash state: gnutlsmpidprintsize wrapnettlepkencrypt gnutlsgenrsaclientkx...