Yes if you are using Spellstrike. Otherwise, probably not. The core rulebook mentions the following when describing how Touch Attacks work (page 186):
If you touch anything or anyone while holding a charge, even unintentionally, the spell discharges.
Cut from the Air states that you make a melee attack roll to deflect a projectile. This implies that you are touching it with your weapon. If you used Spellstrike to make the attack, and missed, then the weapon was still holding the charge. It discharges the spell when it touches the projectile.
But if you are just using Spell Combat without Spellstrike, then your spell charge and melee weapon are separate attacks, probably with different hands. You can use your melee weapon to perform Cut from the Air, and not the hand with the held charge. In this case, you could reasonably say that you didn't make the touch attack against the projectile, meaning that the spell was not discharged. However, this is somewhat open to interpretation; if the GM says that "touch anything" means "touch anything with any body part", then the spell would actually be discharged, regardless of which hand you use.