check camera is supported

[khaledannajar]

In this class: CaptureBarcodesViewController
I get this error:
Uncaught Exception: *** Can't add <AVCaptureDeviceInput: 0x6eb330 [(null)]> because the device does not support AVCaptureSessionPresetMedium. Use -[AVCaptureDevice supportsAVCaptureSessionPreset:].
2014-07-08 17:03:23.075 XXXXXXXXYYYY[2439:707] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* Can't add <AVCaptureDeviceInput: 0x6eb330 [(null)]> because the device does not support AVCaptureSessionPresetMedium. Use -[AVCaptureDevice supportsAVCaptureSessionPreset:].'

I

[khaledannajar]

I fixed that by adding a check that the device has a camera as some versions of iPad does not have a camera.