OSV-2026-301 Use-of-uninitialized-value in pcpp::IPv6Extension::getExtensionLen

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=486705308 Crash type: Use-of-uninitialized-value Crash state: pcpp::IPv6Extension::getExtensionLen pcpp::IPv6Layer::parseExtensions pcpp::IPv6Layer::IPv6Layer...