Cascading Force Wave reads: "...you may pay 3 mana to Push a different creature in that zone one zone in any direction, and repeat this process."
No mention of targeting the different creature, so only the initial creature is ever targeted by anything. Nullify specifically says it only triggers when the creature it's attached to is targeted by an Incantation. Since the Mage is not being targeted by an incantation, the Nullify does not trigger.
Basically what Enti said.