about:blank 标签问题

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
    if([request.URL.absoluteString containsString:@"about:blank"]){
        return NO;
    }
    if([request.mainDocumentURL.absoluteString containsString:@"alipay.com"]){
        [[UIApplication sharedApplication] openURL:request.mainDocumentURL];
    }
    return YES;
}