Merge pull request #108 from ferhatozduran/bug/long-press-nil-index-path

Fix for crash in Swift when long pressing an empty area.

Author: lxcid

LXReorderableCollectionViewFlowLayout/LXReorderableCollectionViewFlowLayout.m

@@ -300,6 +300,10 @@ - (void)handleLongPressGesture:(UILongPressGestureRecognizer *)gestureRecognizer
         case UIGestureRecognizerStateBegan: {
             NSIndexPath *currentIndexPath = [self.collectionView indexPathForItemAtPoint:[gestureRecognizer locationInView:self.collectionView]];
 
+            if (currentIndexPath == nil) {
+                return;
+            }
+            
             if ([self.dataSource respondsToSelector:@selector(collectionView:canMoveItemAtIndexPath:)] &&
                ![self.dataSource collectionView:self.collectionView canMoveItemAtIndexPath:currentIndexPath]) {
                 return;