He flapped once. And that came after he had been fouled just a second before, which made him drop the ball.
Szczesny has been almost as consistent as Koscielny and Mertesacker this season and has probably earned us more points than anyone. He has one dodgy moment in twenty games and he gets criticised. It seems sometimes that Arsenal fans think a player has to be flawless all season to be deserving of praise.