small fix regarding scrollToIndexPath (#1642) close #1640

Author: IceFloe

JSQMessagesViewController/Controllers/JSQMessagesViewController.m

@@ -465,7 +465,10 @@ - (void)scrollToIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated
     //  if last message is too long, use scroll position bottom for better appearance, else use top
     //  possibly a UIKit bug, see #480 on GitHub
     CGSize cellSize = [self.collectionView.collectionViewLayout sizeForItemAtIndexPath:indexPath];
-    CGFloat maxHeightForVisibleMessage = CGRectGetHeight(self.collectionView.bounds) - self.collectionView.contentInset.top - CGRectGetHeight(self.inputToolbar.bounds);
+    CGFloat maxHeightForVisibleMessage = CGRectGetHeight(self.collectionView.bounds) -
+                                         self.collectionView.contentInset.top -
+                                         self.collectionView.contentInset.bottom -
+                                         CGRectGetHeight(self.inputToolbar.bounds);
     UICollectionViewScrollPosition scrollPosition = (cellSize.height > maxHeightForVisibleMessage) ? UICollectionViewScrollPositionBottom : UICollectionViewScrollPositionTop;
 
     [self.collectionView scrollToItemAtIndexPath:indexPath