Lierally "мало ли что ..." is a rhetoric question: "whether there are few things that ...?" implying that there are many such things and we can't even guess which one of them really took place.

"Мало ли что." separately means "everything can happen", in the context it can be "just in case": "возьму пулемет, а то мало ли что." - I'll take a machine gun just in case (because everything can happen).