adam federici 's error gave arsenal a 2-1 victory in fa cup semi-final .
federici fumbled alexis sanchez 's shot - allowing it to go through his legs .
federici left the pitch in tears and apolgised for his error after the game .
fa cup final is on may 30 - same day federici will marry his girlfriend .
there is no suggestion , however , that he let the goal in on purpose .