libc++abi.dylib: terminating with uncaught exception of type NSException - Xcode 8
<p>I'm working with the storyboard and swift 3 on xCode 8 and I get the following error: </p>

<blockquote>
  <p>libc++abi.dylib: terminating with uncaught exception of type NSException
  (lldb) </p>
</blockquote>

<p>here is the complete error log:</p>

<pre><code>    2016-11-03 17:49:13.614 SidebarMenu[14577:867114] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[&lt;SidebarMenu.PopOverViewController 0x7fe4aa0401c0&gt; setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key btn3_leftTapped.'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010beda34b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010b93b21e objc_exception_throw + 48
    2   CoreFoundation                      0x000000010beda299 -[NSException raise] + 9
    3   Foundation                          0x000000010b44b2ff -[NSObject(NSKeyValueCoding) setValue:forKey:] + 291
    4   UIKit                               0x000000010cba78c3 -[UIViewController setValue:forKey:] + 88
    5   UIKit                               0x000000010ce1bbe6 -[UIRuntimeOutletConnection connect] + 109
    6   CoreFoundation                      0x000000010be7f590 -[NSArray makeObjectsPerformSelector:] + 256
    7   UIKit                               0x000000010ce1a56a -[UINib instantiateWithOwner:options:] + 1867
    8   UIKit                               0x000000010cbadff5 -[UIViewController _loadViewFromNibNamed:bundle:] + 386
    9   UIKit                               0x000000010cbae917 -[UIViewController loadView] + 177
    10  UIKit                               0x000000010cbaec4c -[UIViewController loadViewIfRequired] + 201
    11  UIKit                               0x000000010cbaf4a0 -[UIViewController view] + 27
    12  UIKit                               0x000000010cbfd3ba -[UINavigationController preferredContentSize] + 198
    13  UIKit                               0x000000010d4ff0a1 -[UIPopoverPresentationController preferredContentSizeDidChangeForChildContentContainer:] + 152
    14  UIKit                               0x000000010cb8d5bc __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 111
    15  UIKit                               0x000000010ca1a8bb _runAfterCACommitDeferredBlocks + 320
    16  UIKit                               0x000000010ca0753f _cleanUpAfterCAFlushAndRunDeferredBlocks + 566
    17  UIKit                               0x000000010ca387ce _afterCACommitHandler + 176
    18  CoreFoundation                      0x000000010be7ee17 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
    19  CoreFoundation                      0x000000010be7ed87 __CFRunLoopDoObservers + 391
    20  CoreFoundation                      0x000000010be63b9e __CFRunLoopRun + 1198
    21  CoreFoundation                      0x000000010be63494 CFRunLoopRunSpecific + 420
    22  GraphicsServices                    0x00000001115b2a6f GSEventRunModal + 161
    23  UIKit                               0x000000010ca0df34 UIApplicationMain + 159
    24  SidebarMenu                         0x000000010af53b5f main + 111
    25  libdyld.dylib                       0x0000000112e2968d start + 1
    26  ???                                 0x0000000000000001 0x0 + 1
)
</code></pre>

<p>The first line of the error message tells me that the error is in the <code>PopOverViewController</code> and than in <code>btn3_leftTapped</code>.
In the PopOverViewController I have connected an Action from the button: </p>

<pre><code>@IBAction func btn3_leftTappedNow(_ sender: AnyObject) {
}
@IBAction func btn3_rightTapped(_ sender: AnyObject) {
    self.dismiss(animated: true){ () -&gt; Void in

        NotificationCenter.default.post(name: NSNotification.Name(rawValue: btn3_rightTappedDone), object: nil, userInfo: nil)

    }
}
</code></pre>

<p>First I thought that i have to delete this connection and then recreate it, but it does not change. Even if I delete the connection and create a new one with a different name like <code>btn3_leftTappedNow</code> I still get the error message shown above. 
I used ctrl + f to search in my .swift file after the phrase but it isn't in my document any more. </p>

<p>I tried Product -> Clean but I still get the error and I have no problem building the app. </p>

<p>What can I do to solve this error?</p>