OSV-2020-1488 Segv on unknown address in llvm::llvm_unreachable_internal

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20787 Crash type: Segv on unknown address Crash state: llvm::llvmunreachableinternal findDefaultInitializer checkDuplicateDefaultInit...