在iOS10上removeAllSubviews后，再调用addArrangedSubview Crash，什么原因？
报错：
Assertion failure in -[FDStackView _layoutEngine_didAddLayoutConstraint:roundingAdjustment:mutuallyExclusiveConstraints:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3600.7.47/NSLayoutConstraint_UIKitAdditions.m:649
invalid mode 'kCFRunLoopCommonModes' provided to CFRunLoopRunSpecific - break on _CFRunLoopError_RunCalledWithInvalidMode to debug. This message will only appear once per execution.
在iOS10上removeAllSubviews后，再调用addArrangedSubview Crash，什么原因？
报错：
Assertion failure in -[FDStackView _layoutEngine_didAddLayoutConstraint:roundingAdjustment:mutuallyExclusiveConstraints:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3600.7.47/NSLayoutConstraint_UIKitAdditions.m:649
invalid mode 'kCFRunLoopCommonModes' provided to CFRunLoopRunSpecific - break on _CFRunLoopError_RunCalledWithInvalidMode to debug. This message will only appear once per execution.