Crash在NSMutableArray+SafeKit.h 的-(void)SKaddObject:(id)anObject方法处

[Ilikewhite]

UIImageView在重置Constraints时，会有很高的概率crash。
我们的代码如下：先清除了自己之前的约束，然后重新增加新的约束，然后-(void)SKaddObject:(id)anObject报错，导致crash

    //经验值条增长动画
    [self.expLineImageView removeConstraints:self.expLineImageView.constraints];
    [self.expLineImageView addConstraint:[NSLayoutConstraint
                                             constraintWithItem:self.expLineImageView
                                                      attribute:NSLayoutAttributeHeight
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:nil
                                                      attribute:0
                                                     multiplier:1
                                                       constant:2]];
    [self.expLineImageView addConstraint:[NSLayoutConstraint
                                             constraintWithItem:self.expLineImageView
                                                      attribute:NSLayoutAttributeWidth
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:nil
                                                      attribute:0
                                                     multiplier:1
                                                       constant:320 * _levelPercent]];