There are no official rules that I know of that handle what happens when a dazed character is involved in a grapple.
My suggestion is that the grapple *not* be automatically broken. Dazed is a very minor incapacitated state. In fact, a dazed character is not truly incapacitated at all. It is just prevented from taking actions for 1 round. Importantly, a dazed creature does not lose any AC. It is able to defend itself. It is able to respond to threats.
It just cannot take any new actions. My interpretation is that a dazed character can respond to outside stimulus, but cannot begin new activities. Accordingly, if a Burly barbarian were grappling a cleric, and that cleric cast blasphemy (dazing the barbarian), the barbarian would not automatically release the cleric. If the cleric wants to get free, it would need to find a way to instigate a grapple check or escape artist check of its own to get free.