use-of-uninitialized-value in tune look behind

use-of-uninitialized-value in tune look behind: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). MemorySanitizer: use-of-uninitialized-value in function tune look behind in file php-src/oniguruma/src/regcomp.c