if someone leaves the game, a bot is put in to join, but that bot cannot act. So if the bot needs to judge a round, the game gets halted and is stuck.

Hello,
This isn't a bug. This bot is here in case you would like to replace this player by another human player. If you find another person, CTRL+R will let you replace the bot.

However, if you don't want this and want to continue the game, kick the bot using CTRL+K, and it will leave, allowing you to continue further.