处理来自设置的地址簿权限 - ＆gt;隐私崩溃

Question

我正在使用以下代码向地址簿请求权限并将其保存到应用程序的UserDefaults。

if (ABAddressBookRequestAccessWithCompletion != NULL)
{
    // we're on iOS 6
    ABAddressBookRef addressBookRef = ABAddressBookCreate();
    ABAddressBookRequestAccessWithCompletion(addressBookRef, ^(bool granted, CFErrorRef error) {
        accessgranted = granted;
        if(accessgranted)
        {
             [self saveaddressbookpermission:accessgranted];
            [NSThread detachNewThreadSelector:@selector(startbgprocess) toTarget:self withObject:nil];
        }
    });
    CFRelease(addressBookRef);

}
else {
    // we're on iOS 5 or older
    accessgranted = YES;
    [self saveaddressbookpermission:accessgranted];
    NSLog(@"in iOS 5");
   [NSThread detachNewThreadSelector:@selector(startbgprocess) toTarget:self withObject:nil];

}

问题是当我尝试使用设置 - ＆gt;常规 - ＆gt;重置 - ＆gt;重置隐私设置时重置位置＆amp;隐私，但如果我尝试从设置 - ＆gt;隐私 - ＆gt;更改隐私设置并从那里关闭权限然后我的应用程序崩溃。我该如何处理这种情况。如果我无法找到任何其他相关信息，请通知我。