Rogue Talent: A slayer can select one of the following rogue talents in place of a slayer talent: bleeding attack*, camouflage, combat trick, fast stealth, finesse rogue, firearm training, grit, hard to fool, lasting poison, powerful sneak, rogue crawl, slow reactions*, snap shot, sniper's eye, surprise attack, swift poison, terrain mastery, trap spotter, unwitting ally, or weapon training. Any talent effects based on rogue level use the slayer's class level. If the rogue talent has a prerequisite , the slayer must fulfill the prerequisite before taking that rogue talent. This talent can be selected multiple times; each time, it grants the slayer a new rogue talent.
One of the options in this list is Grit. It's full description is:
Prerequisite: Firearm training talent
Benefit: A rogue with this talent gains the Amateur Gunslinger feat and one grit feat of her choice. She must fulfill the prerequisites of the grit feat in order to choose it.
The Amateur Gunslinger feat says the following:
Prerequisite: You have no levels in a class that has the grit class feature.
Special: If you gain levels in a class that grants the grit class feature, you can immediately trade this feat for the Extra Grit feat.
Does the prerequisite of the Amateur Gunslinger preclude a multiclassed Gunslinger/Slayer from taking the Grit rogue talent in order to gain an additional arbitrary grit feat? If not, how does this selection interact with Amateur Gunslinger? Does the character in question simply not gain Amateur Gunslinger, or does he/she immediately swap it for Extra Grit since he/she already has levels in a class that grants the grit class feature?