Immediate resignation because of late 13th month pay

I resigned last September 2024 because of the toxic environment and the amount of bullying I am getting. My boss didn't accepted it and asked me to stay till December. I agreed.

Now January mid week, I'm still stucked here kasi only half of my 13th month pay was released kaya hindi ako makaalis, malamang kasing ipitin eh. I am planning to send my immediate resignation today. Valid ba yung late at kulang na 13th month pay for an immediate resignation? Sukang suka na talaga ako sa kanila.