Is there a way to cancel a beam attack on iPad?

When playing on the tablet, once you start drawing the path of the beam to perform an attack, when the beam is already charged and ready, is there a way to cancel the attack?

The game auto-pauses while selecting the position of the beam, but sometimes you realize that there is something that you want to do first so you need to stop that attack. However when you raise your fingers from the screen, the action resumes automatically giving you no option to pause or cancel the beam attack.

Its a bit awkward with your hands but what i do is turn my ipad to standby or press the home button this will cancel the action!