OSV-2020-783 UNKNOWN READ in wabt::BinaryReaderIR::OnFunctionSymbol

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20364 Crash type: UNKNOWN READ Crash state: wabt::BinaryReaderIR::OnFunctionSymbol wabt::BinaryReader::ReadLinkingSection wabt::BinaryReader::ReadCustomSection...