It's the right call. Referees just go by the book in cases like this. No ref would try to find out what exactly did Handanovic see there, nor they should. Yeah, it's very likely Kalulu didn't have any affect on him and he would have conceded anyways but that's how it always works.
By the way, in this picture it seems that he was obscured, judging by the way he stands. Trying to get a better look at the ball there. One sec later he's completely blocked by him. It's the right call.