STTwitter return nil iOS

Question

I'm using STTwitter Library (latest version) and trying to get tweets with authenticating by oAuth and specifically using the Application Only authentication which provide the bearer token. I used the example code provided on GitHub but I do not getting neither success or error on the log out. This is my code :

STTwitterAPI *twitter = [STTwitterAPI twitterAPIAppOnlyWithConsumerKey:@"XXX"
                                                    consumerSecret:@"XXX"];
[twitter verifyCredentialsWithSuccessBlock:^(NSString *bearerToken) {

[twitter getUserTimelineWithScreenName:@"sttwitter"
                          successBlock:^(NSArray *statuses) {
    NSLog("successBlock : ", statuses);
} errorBlock:^(NSError *error) {
    NSLog("errorBlock : ", error);
}];
} errorBlock:^(NSError *error) {
NSLog("errorBlock : ", error);
}];

Any help will be appreciated. I'm unable to find other twitter library specially for the api v1.1.