ios8.0 ipad UIImagePickerController

Warning:
Attempt
to present <UIImagePickerController:
0x7c0ae400>
on <CAGUCreateContactViewController:
0x7bf61a00>
which is
already presenting (null)

if([[[UIDevice currentDevice] systemVersion] floatValue]>=8.0)
{
[[NSOperationQueue mainQueue] addOperationWithBlock:^{

[self presentViewController:cameraUI animated:NO completion:nil];
}];

}
else{

[controller presentViewController:cameraUI animated:NO completion:nil];
}