OSV-2021-308 Heap-buffer-overflow in flatbuffers::JsonPrinter::GenFieldOffset

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=30468 Crash type: Heap-buffer-overflow READ 4 Crash state: flatbuffers::JsonPrinter::GenFieldOffset flatbuffers::JsonPrinter::GenStruct flatbuffers::GenerateText...