OSV-2020-45 Use-of-uninitialized-value in pcpp::tbp_my_own_strnlen

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=22829 Crash type: Use-of-uninitialized-value Crash state: pcpp::tbpmyownstrnlen pcpp::HeaderField::HeaderField pcpp::TextBasedProtocolMessage::parseFields...