Error when enqueuing buffer from callback Wit.ai SDK for iOS

Question

I'm new to iOS and I'm writing my first application using wit.ai SDK (following this guide https://wit.ai/docs/ios/3.1.1/quickstart).

I can run my app and send a command (that I'll find in my wit.ai inbox) but then the app craches.

Here is my code:

AppDelegate.h

#import <UIKit/UIKit.h> 
@interface AppDelegate : UIResponder <UIApplicationDelegate> 
@property (strong, nonatomic) UIWindow *window;
@end

AppDelegate.m

#import "AppDelegate.h"
#import <Wit/Wit.h>

@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
[Wit sharedInstance].accessToken = @"ASW7RE57SOSZLTNBAM6HQ53QAWXSROOI";
[Wit sharedInstance].detectSpeechStop = WITVadConfigDetectSpeechStop;
// Override point for customization after application launch.
return YES;
}

ViewController.h

#import <UIKit/UIKit.h>
#import <Wit/Wit.h>

@interface ViewController : UIViewController <WitDelegate>


@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController {
    UILabel *labelView;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // set the WitDelegate object
    [Wit sharedInstance].delegate = self;

    // create the button
    CGRect screen = [UIScreen mainScreen].bounds;
    CGFloat w = 100;
    CGRect rect = CGRectMake(screen.size.width/2 - w/2, 60, w, 100);

    WITMicButton* witButton = [[WITMicButton alloc] initWithFrame:rect];
    [self.view addSubview:witButton];

    // create the label
    labelView = [[UILabel alloc] initWithFrame:CGRectMake(0, 200, screen.size.width, 50)];
    labelView.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:labelView];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)witDidGraspIntent:(NSArray *)outcomes entities:(NSDictionary *)entities body:(NSString *)body error:(NSError*)e {
    if (e) {
        NSLog(@"[Wit] error: %@", [e localizedDescription]);
        return;
    }
    NSDictionary *firstOutcome = [outcomes objectAtIndex:0];
    NSString *intent = [firstOutcome objectForKey:@"intent"];

    labelView.text = [NSString stringWithFormat:@"intent = %@", intent];

    [self.view addSubview:labelView];
}

@end

Here are the errors I get:

2015-01-12 22:24:21.419 FirstApp[11199:775307] WITVad init 2015-01-12 22:24:27.789 FirstApp[11199:775513] Error when enqueuing buffer from callback: -66632 2015-01-12 22:24:27.790 FirstApp[11199:775513] Error when enqueuing buffer from callback: -66632 2015-01-12 22:24:27.790 FirstApp[11199:775513] Error when enqueuing buffer from callback: -66632 2015-01-12 22:24:27.790 FirstApp[11199:775513] Error when enqueuing buffer from callback: -66632 2015-01-12 22:24:27.790 FirstApp[11199:775513] Error when enqueuing buffer from callback: -66632 2015-01-12 22:24:36.442 FirstApp[11199:775307] -[NSCFString objectAtIndex:]: unrecognized selector sent to instance 0x7f8da0c60c30 2015-01-12 22:24:36.755 FirstApp[11199:775307] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString objectAtIndex:]: unrecognized selector sent to instance 0x7f8da0c60c30' *** First throw call stack: ( 0 CoreFoundation 0x0000000105bd0f35 __exceptionPreprocess + 165 1 libobjc.A.dylib 0x000000010548fbb7 objc_exception_throw + 45 2 CoreFoundation 0x0000000105bd804d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205 3 CoreFoundation 0x0000000105b3027c ___forwarding_ + 988 4 CoreFoundation 0x0000000105b2fe18 _CF_forwarding_prep_0 + 120 5 FirstApp 0x00000001034778bd -[ViewController witDidGraspIntent:entities:body:error:] + 253 6 FirstApp 0x000000010347a705 -[Wit processMessage:] + 535 7 FirstApp 0x000000010347a3a2 -[Wit gotResponse:error:] + 67 8 FirstApp 0x000000010347a3f3 -[Wit gotResponse:error:customData:] + 62 9 FirstApp 0x0000000103478549 -[WITRecordingSession gotResponse:error:] + 196 10 FirstApp 0x000000010347b726 39-[WITUploader startRequestWithContext:]_block_invoke + 708 11 CFNetwork 0x0000000106781935 __67+[NSURLConnection sendAsynchronousRequest:queue:completionHandler:]_block_invoke_2 + 155 12 Foundation 0x000000010360201f __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK + 7 13 Foundation 0x0000000103541db2 -[NSBlockOperation main] + 98 14 Foundation 0x0000000103524384 -[NSOperationInternal _start:] + 645 15 Foundation 0x0000000103523f93 __NSOQSchedule_f + 184 16 libdispatch.dylib 0x0000000106eec7f4 _dispatch_client_callout + 8 17 libdispatch.dylib 0x0000000106ed58fb _dispatch_main_queue_callback_4CF + 949 18 CoreFoundation 0x0000000105b38fe9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE + 9 19 CoreFoundation 0x0000000105afbeeb __CFRunLoopRun + 2043 20 CoreFoundation 0x0000000105afb486 CFRunLoopRunSpecific + 470 21 GraphicsServices 0x0000000107f739f0 GSEventRunModal + 161 22 UIKit 0x00000001039d2420 UIApplicationMain + 1282 23 FirstApp 0x0000000103477e53 main + 115 24 libdyld.dylib 0x0000000106f21145 start + 1 25 ??? 0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException

Thanks for your help.