heap-buffer-overflow in utf16CountUtf8Bytes

heap-buffer-overflow in utf16CountUtf8Bytes: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). AddressSanitizer: heap-buffer-overflow in function utf16CountUtf8Bytes in file poppler/poppler/UTF.cc