What is “Terminating in response to backboardd's termination”?-Collection of common programming errors

i use a piece of code for drop shadow on a view with help of slider. Slider is set -15 to 15. This code works awesome when slider.value is positive but app stop working if its negative. the crash log is weird “Terminating in response to backboardd’s termination”.

i got this log first time.Whats is that?

here is my code.

    childViews.layer.shadowColor = [[UIColor blackColor] CGColor];
    childViews.layer.shadowOffset = CGSizeMake(slide,slide);
    childViews.layer.shadowOpacity = 1.0;
    childViews.layer.shadowRadius=10;
    childViews.layer.masksToBounds = NO;
    childViews.layer.shouldRasterize = YES;