Whenever you ask questions about the Dream and the dreamer, you must bear in mind that not anything which appears in consciousness is real (consciousness itself is not real).

So, the Dream is not real, it is an illusion. The dreamer of the Dream (and in the Dream) is no more real than the Dream. This is why it is said that life is an illusion.

An unreal Dream, then, is being dreamed by an unreal dreamer. Is anything actually happening in reality? No. not anything actually happens in reality.

So, your next question might be: where is this non-happening occurring?

It is not occurring. An occurrence takes place at some time, in some space; and an occurrence is the effect of some cause. All phenomenon are unreal, and thus do not truly exist; this includes the phenomena of time, space and cause and effect.

The question you ask is within the Dream; not anything in the dream is real. What answer will the dreamer—who does not actually exist—get, that will not itself simply be within the dream?

In other words, is there any thing that matters? No, not anything. This you can come to know—within the Dream.