Lovers Katrina Kaif and Ranbir Kapoor are back together onscreen in Ayan Mukerjee’s next flick.A source tells, “Ayan was going back and forth about who to cast in the film. It was a very difficult period given Ranbir’s relationship with Kat was on the rocks. They were going through a rough phase and it wasn’t clear if they would want to work with each other immediately or take a short break. Ayan