OSV-2021-1385 Heap-buffer-overflow in Assimp::BaseImporter::ConvertToUTF8

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=39339 Crash type: Heap-buffer-overflow READ 1 Crash state: Assimp::BaseImporter::ConvertToUTF8 Assimp::BaseImporter::TextFileToBuffer Assimp::OpenGEX::OpenGEXImporter::InternReadFile...