Is it an automatic split between two players, if there is an ace high flush on the table and one player has no hearts in his hand ?
When there are 5 Cards of one suit on the board it will be a split in case no other player has a card of that suit which is higher than the lowest card of the suit on the board.
If the board shows already a straight flush, you wont win even if you hold the ace of that suit. in case you wont make the royal flush using that ace...
Since all cards of the same suit, there is no full house possible.