UIWebview failed for URL error

I want to listen the webview and do something with the opened url. I do this with this delegate method.

Code:

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {

    NSString *currentLink = request.URL.absoluteString;
  
  
    if ([currentLink containsString:@"close"]) {      
        [self closeTheAdvView];
    }
  
    return YES;
}

1- i try to click a button inside the webview. It works in iOS9 but not in iOS8. How can i make it clickable in iOS 8 as well ?

2- when i click a button inside the webview it opens a new url(e.g:close.com). when i get that link then i will hide the webview. but when i click the button then it gives an error in log screen like

what can be wrong here ?