The mage would cast the spell (you complete all of the steps of casting a spell and you still have to pay the cost of the attack spell), the attack just wouldn't land if you failed the daze roll.
I can't give you an official answer in the sense that I am not an official source, but I can point you to the relevant rules references.
On page 14 of the rulebook it says that:
Attack spells allow your spell caster to attack a target in the arena. When the spell resolves, you make the attack on the target.
On page 3 of the rules supplement, it gives the phases used for all types of attacks. It indicates that you must roll for daze when making a single target ranged attack (and all other types of attacks except damage barriers).
Alternatively, you could look at the rulebook on page 23, where it says:
When you cast an attack spell, it is both a spell and an attack. First, you must follow all steps for casting, just like any spell. Then, if the spell is not countered, you must resolve the attack, following the steps for attacking. The target of the attack is always the same as the target you chose when you cast the spell. Attack spells will not show a “quick” or “full” action icon on the attack bar, because the quick or full action required to make the attack occurs when the spell is cast. Also, the range of the attack is determined by the range of the spell, so no range is shown on the attack bar. They also do not have an “attack name” on the bar, because the name of the attack is the same as the spell.
Which means that you treat an attack spell just like any other attack. You must go through all of the steps of an attack, including the possibility of missing due to a daze condition. You have to go through the declare attack step, and at the end of the declare attack step, if you have a daze condition, you must check to see if you miss.