Apparently, in the song Deepika is drunk and dancing wildly in a dhabha on the highway. She climbs on to the table and while dancing falls recklessly into Saif's arms. In one particular take, Deepika leaned back to fall into Saif's arms but instead fell off the table which was on a raised platform 6-7 feet off the ground.
Luckily, Saif's quick reflexes caught Deepika's clothes and the two tumbled off the platform together, with no injuries. Everyone was shocked and worried at the fall, but Deepika laughed the whole thing off and was ready to do the next take.... That's our girl!