Copy attributes before modifying in layout (#1868). Close #1218

Author: algrid

JSQMessagesViewController/Layout/JSQMessagesCollectionViewFlowLayout.m

@@ -270,7 +270,7 @@ - (void)prepareLayout
         CGFloat padding = -100.0f;
         CGRect visibleRect = CGRectInset(self.collectionView.bounds, padding, padding);
 
-        NSArray *visibleItems = [super layoutAttributesForElementsInRect:visibleRect];
+        NSArray *visibleItems = [[NSArray alloc] initWithArray:[super layoutAttributesForElementsInRect:visibleRect] copyItems:YES];
         NSSet *visibleItemsIndexPaths = [NSSet setWithArray:[visibleItems valueForKey:NSStringFromSelector(@selector(indexPath))]];
 
         [self jsq_removeNoLongerVisibleBehaviorsFromVisibleItemsIndexPaths:visibleItemsIndexPaths];
@@ -281,7 +281,7 @@ - (void)prepareLayout
 
 - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
 {
-    NSArray *attributesInRect = [[super layoutAttributesForElementsInRect:rect] copy];
+    NSArray *attributesInRect = [[NSArray alloc] initWithArray:[super layoutAttributesForElementsInRect:rect] copyItems:YES];
 
     if (self.springinessEnabled) {
         NSMutableArray *attributesInRectCopy = [attributesInRect mutableCopy];