[<UIView 0x89bfd40> setValue:forUndefinedKey:] - ios

Question

Another problem that is causing my build to succeed, then terminate. As follows:
Error:
2013-09-30 20:21:23.708 The Solver[2566:a0b] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UIView 0x89bfd40> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key welcomeBeta.'
*** First throw call stack:
(
0 CoreFoundation 0x023615e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x014bf8b6 objc_exception_throw + 44
2 CoreFoundation 0x023f16a1 -[NSException raise] + 17
3 Foundation 0x00f73c2e -[NSObject(NSKeyValueCoding) setValue:forUndefinedKey:] + 282
4 Foundation 0x00edff3b _NSSetUsingKeyValueSetter + 88
5 Foundation 0x00edf493 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 267
6 UIKit 0x0008f97b -[UIView(CALayerDelegate) setValue:forKey:] + 168
7 Foundation 0x00f4194a -[NSObject(NSKeyValueCoding) setValue:forKeyPath:] + 412
8 UIKit 0x002c6cd5 -[UIRuntimeOutletConnection connect] + 106
9 libobjc.A.dylib 0x014d17d2 -[NSObject performSelector:] + 62
10 CoreFoundation 0x0235cb6a -[NSArray makeObjectsPerformSelector:] + 314
11 UIKit 0x002c582e -[UINib instantiateWithOwner:options:] + 1417
12 UIKit 0x00137c95 -[UIViewController _loadViewFromNibNamed:bundle:] + 280
13 UIKit 0x0013843d -[UIViewController loadView] + 302
14 UIKit 0x0013873e -[UIViewController loadViewIfRequired] + 78
15 UIKit 0x00138c44 -[UIViewController view] + 35
16 UIKit 0x000615ad -[UIWindow addRootViewControllerViewIfPossible] + 66
17 UIKit 0x00061947 -[UIWindow _setHidden:forced:] + 312
18 UIKit 0x00061bdd -[UIWindow _orderFrontWithoutMakingKey] + 49
19 UIKit 0x0006c44a -[UIWindow makeKeyAndVisible] + 65
20 UIKit 0x0001f8e0 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1851
21 UIKit 0x00023fb8 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 824
22 UIKit 0x0003842c -[UIApplication handleEvent:withNewEvent:] + 3447
23 UIKit 0x00038999 -[UIApplication sendEvent:] + 85
24 UIKit 0x00025c35 _UIApplicationHandleEvent + 736
25 GraphicsServices 0x022bf2eb _PurpleEventCallback + 776
26 GraphicsServices 0x022bedf6 PurpleEventCallback + 46
27 CoreFoundation 0x022dcdd5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
28 CoreFoundation 0x022dcb0b __CFRunLoopDoSource1 + 523
29 CoreFoundation 0x023077ec __CFRunLoopRun + 2156
30 CoreFoundation 0x02306b33 CFRunLoopRunSpecific + 467
31 CoreFoundation 0x0230694b CFRunLoopRunInMode + 123
32 UIKit 0x000236ed -[UIApplication _run] + 840
33 UIKit 0x0002594b UIApplicationMain + 1225
34 The Solver 0x000033dd main + 141
35 libdyld.dylib 0x059a5725 start + 0
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
Code for UIControllerView with welcomeBeta (Button)
WelcomeUI.h:
#import <UIKit/UIKit.h>
#interface WelcomeUI : UIViewController
#property (weak, nonatomic) IBOutlet UIButton *welcomeStart;
#property (weak, nonatomic) IBOutlet UIButton *welcomeBeta;
#end
WelcomeUI.m:
#import "WelcomeUI.h"
#interface WelcomeUI ()
#end
#implementation WelcomeUI
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
Please let me know where I'm going wrong. Also explain in detail as I'm new to objective-c and Xcode.