__NSStackBlock__ isEqualToString: issue - objective-c

Question

I am experimenting with this code.
In one of viewController's I am using next snippet:
- (BOOL)textView:(UITextView *)textView1 shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
if([text isEqualToString:#"\n"])
{
[textView resignFirstResponder];
return NO;
}
return YES;
}
I found in web to dismissing the keyboard by pressing returnButton. It works well when I am calling it from this viewController. In root KLNoteViewController I am adding notification in handle state changes-method:
- (void) setState:(KLControllerCardState)state animated:(BOOL) animated
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"refresh" object:self];
if (animated)
{
[UIView animateWithDuration:self.noteViewController.cardAnimationDuration animations:^{
[self setState:state animated:NO];
}];
return;
}
//Full Screen State
if (state == KLControllerCardStateFullScreen)
{
[self expandCardToFullSize: animated];
[self setYCoordinate: 0];
}
//Default State
else if (state == KLControllerCardStateDefault)
{
[self shrinkCardToScaledSize: animated];
[self setYCoordinate: originY];
}
//Hidden State - Bottom
else if (state == KLControllerCardStateHiddenBottom)
{
//Move it off screen and far enough down that the shadow does not appear on screen
[self setYCoordinate: self.noteViewController.view.frame.size.height + abs(self.noteViewController.cardShadowOffset.height)*3];
}
//Hidden State - Top
else if (state == KLControllerCardStateHiddenTop)
{
[self setYCoordinate: 0];
}
//Notify the delegate of the state change (even if state changed to self)
KLControllerCardState lastState = self.state;
//Update to the new state
[self setState:state];
//Notify the delegate
if ([self.delegate respondsToSelector:#selector(controllerCard:didChangeToDisplayState:fromDisplayState:)]) {
[self.delegate controllerCard:self
didChangeToDisplayState:state fromDisplayState: lastState];
}
}
and add adding observer:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(dismissKeyboard) name:#"refresh" object:nil];
in every viewControllers -viewDidLoad. So when this observer is used with UITextField everything works fine, in viewController when I am using UIText View I have crash with log:
[NSStackBlock isEqualToString:]: unrecognized selector sent to
instance 0xbfffd228
I searched in web but found only two links with explanation of what is the NSStackBlock is and they are not informative well for me to solve the problem. Can somebody explain what it can be?