In maps/PokemonFanClub.asm, PokemonFanClubChairmanScript checks this event:
checkevent EVENT_LISTENED_TO_FAN_CLUB_PRESIDENT_BUT_BAG_WAS_FULL
iftrue .HeardSpeechButBagFull
However, listening to his speech while your Bag is full doesn't actually set this event:
verbosegiveitem RARE_CANDY
iffalse .BagFull