Merge pull request #250 from sgraesser/master

bug: Fixed library crash after adding image attachment #237

Sources/Plugins/AttachmentManager/AttachmentManager.swift

@@ -202,14 +202,21 @@ extension AttachmentManager: UICollectionViewDataSource, UICollectionViewDelegat
 
     final public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
 
-        if let customSize = self.dataSource?.attachmentManager(self, sizeFor: self.attachments[indexPath.row], at: indexPath.row){
-            return customSize
-        }
-
         var height = attachmentView.intrinsicContentHeight
         if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
             height -= (layout.sectionInset.bottom + layout.sectionInset.top + collectionView.contentInset.top + collectionView.contentInset.bottom)
         }
+
+        // Prevent out of range error when the AttachmentCell has not been added the attachment array
+        if indexPath.row == attachments.count && showAddAttachmentCell {
+            return CGSize(width: height, height: height)
+        }
+
+        let attachment = self.attachments[indexPath.row]
+        if let customSize = self.dataSource?.attachmentManager(self, sizeFor: attachment, at: indexPath.row){
+            return customSize
+        }
+
         return CGSize(width: height, height: height)
     }