title: 'Unable to create description in descriptionForLayoutAttribute_layoutItem_coefficient. Something is nil'
body: <p>First, I got 3 different UIViews to replace the detail view in Split View Controller on iPad storyboard</p>
  
  <p>It runs on well on iOS8 iPad. But when I load one of the detail views, the app crashes when running in iOS7 and iOS 6 Simulator.</p>
  
  <p>I only assume it is because of Auto layout on my Storyboard.</p>
  
  <p>Does anyone know how to fix it?</p>
  
  <pre><code>2014-09-25 04:15:19.705 PSTappsperance[48327:60b] Pad AppDelegate ########
  2014-09-25 04:15:27.869 PSTappsperance[48327:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to create description in descriptionForLayoutAttribute_layoutItem_coefficient. Something is nil'
  *** First throw call stack:
  (
  0   CoreFoundation                      0x0000000110a5c495 __exceptionPreprocess + 165
  1   libobjc.A.dylib                     0x00000001107af99e objc_exception_throw + 43
  2   CoreFoundation                      0x0000000110a5c2ad +[NSException raise:format:] + 205
  3   Foundation                          0x00000001104ec548 descriptionForLayoutAttribute_layoutItem_coefficient + 145
  4   Foundation                          0x00000001104ec3bc -[NSLayoutConstraint equationDescription] + 216
  5   Foundation                          0x00000001104ec831 -[NSLayoutConstraint description] + 297
  6   CoreFoundation                      0x0000000110a1d1b9 -[NSArray descriptionWithLocale:indent:] + 345
  7   Foundation                          0x000000011037e14e _NSDescriptionWithLocaleFunc + 64
  8   CoreFoundation                      0x00000001109e1244 __CFStringAppendFormatCore + 7252
  9   CoreFoundation                      0x0000000110a1f913 _CFStringCreateWithFormatAndArgumentsAux + 115
  10  CoreFoundation                      0x0000000110a7fa5b _CFLogvEx + 123
  11  Foundation                          0x00000001103ae276 NSLogv + 79
  12  Foundation                          0x00000001103ae20a NSLog + 148
  13  UIKit                               0x000000010f927097 -[UIView(UIConstraintBasedLayout_EngineDelegate) engine:willBreakConstraint:dueToMutuallyExclusiveConstraints:] + 62
  14  Foundation                          0x00000001104e32ac -[NSISEngine handleUnsatisfiableRowWithHead:body:usingInfeasibilityHandlingBehavior:mutuallyExclusiveConstraints:] + 521
  15  Foundation                          0x00000001104e49b1 -[NSISEngine tryUsingArtificialVariableToAddConstraintWithMarker:rowBody:usingInfeasibilityHandlingBehavior:mutuallyExclusiveConstraints:] + 353
  16  Foundation                          0x000000011039c26b -[NSISEngine tryToAddConstraintWithMarker:expression:integralizationAdjustment:mutuallyExclusiveConstraints:] + 663
  17  Foundation                          0x00000001104ed180 -[NSLayoutConstraint _addLoweredExpression:toEngine:integralizationAdjustment:lastLoweredConstantWasRounded:mutuallyExclusiveConstraints:] + 275
  18  Foundation                          0x00000001103981b0 -[NSLayoutConstraint _addToEngine:integralizationAdjustment:mutuallyExclusiveConstraints:] + 204
  19  UIKit                               0x000000010f923f41 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 413
  20  Foundation                          0x00000001104e529a -[NSISEngine withBehaviors:performModifications:] + 119
  21  UIKit                               0x000000010f923d7d __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 401
  22  UIKit                               0x000000010f923bc3 -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
  23  UIKit                               0x000000010f923e57 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 179
  24  Foundation                          0x00000001104e529a -[NSISEngine withBehaviors:performModifications:] + 119
  25  UIKit                               0x000000010f923d7d __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 401
  26  UIKit                               0x000000010f923bc3 -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
  27  UIKit                               0x000000010f3ab975 __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 95
  28  Foundation                          0x00000001104e529a -[NSISEngine withBehaviors:performModifications:] + 119
  29  UIKit                               0x000000010f3ab889 -[UIView(Hierarchy) _postMovedFromSuperview:] + 321
  30  UIKit                               0x000000010f3b52ac -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1508
  31  UIKit                               0x000000010f632778 -[UINavigationTransitionView transition:fromView:toView:] + 454
  32  UIKit                               0x000000010f6325b0 -[UINavigationTransitionView transition:toView:] + 25
  33  UIKit                               0x000000010f46f4d7 -[UINavigationController _startTransition:fromViewController:toViewController:] + 2893
  34  UIKit                               0x000000010f46f787 -[UINavigationController _startDeferredTransitionIfNeeded:] + 547
  35  UIKit                               0x000000010f470238 -[UINavigationController __viewWillLayoutSubviews] + 43
  36  UIKit                               0x000000010f58a895 -[UILayoutContainerView layoutSubviews] + 202
  37  UIKit                               0x000000010f3b7993 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 354
  38  QuartzCore                          0x000000011427c802 -[CALayer layoutSublayers] + 151
  39  QuartzCore                          0x0000000114271369 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 363
  40  QuartzCore                          0x00000001142711ea _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
  41  QuartzCore                          0x00000001141e4fb8 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 252
  42  QuartzCore                          0x00000001141e6030 _ZN2CA11Transaction6commitEv + 394
  43  QuartzCore                          0x00000001141e669d _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 89
  44  CoreFoundation                      0x0000000110a27dc7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
  45  CoreFoundation                      0x0000000110a27d37 __CFRunLoopDoObservers + 391
  46  CoreFoundation                      0x0000000110a07522 __CFRunLoopRun + 946
  47  CoreFoundation                      0x0000000110a06d83 CFRunLoopRunSpecific + 467
  48  GraphicsServices                    0x0000000112dbdf04 GSEventRunModal + 161
  49  UIKit                               0x000000010f357e33 UIApplicationMain + 1010
  50  PSTappsperance                      0x000000010f092653 main + 115
  51  libdyld.dylib                       0x00000001114b05fd start + 1
  52  ???                                 0x0000000000000001 0x0 + 1
  )libc++abi.dylib: terminating with uncaught exception of type NSException
  </code></pre>