fix(ios): edge case crash on collection view refresh

Author: farfromrefug

packages/collectionview/platforms/ios/src/UICollectionViewCacheDelegateFlowLayout.m

@@ -18,19 +18,21 @@ - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollection
 - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
 {
   NSInteger index = indexPath.row;
-  if (index < [self.cachedSizes count]) {
-      NSValue* value =  [self.cachedSizes objectAtIndex:indexPath.row];
+  NSInteger count = [self.cachedSizes count];
+  if (index < count) {
+      NSValue* value =  [self.cachedSizes objectAtIndex:index];
       if (value != nil && !CGSizeEqualToSize([value CGSizeValue], CGSizeZero)) {
           return [value CGSizeValue];
       }
-    CGSize size = [self collectionView:collectionView layout:collectionViewLayout computedSizeForItemAtIndexPath:indexPath];
+  }
+  CGSize size = [self collectionView:collectionView layout:collectionViewLayout computedSizeForItemAtIndexPath:indexPath];
+  count = [self.cachedSizes count];
+  if (index < count) {
     [self.cachedSizes replaceObjectAtIndex:indexPath.row withObject:[NSValue valueWithCGSize:size]];
-    return size;
   } else {
-    CGSize size = [self collectionView:collectionView layout:collectionViewLayout computedSizeForItemAtIndexPath:indexPath];
     [self.cachedSizes addObject:[NSValue valueWithCGSize:size]];
-    return size;
   }
+  return size;
 }
 
 @end