From a02dcfd9dce4a9261c893ced22f94b0019e7ecfc Mon Sep 17 00:00:00 2001
From: Valerii Chevtaev <valerii.chevtaev@corp.badoo.com>
Date: Mon, 13 Mar 2017 11:06:49 +0000
Subject: [PATCH] Return empty layout model is layout delegate is empty.

---
 .../Collaborators/ChatCollectionViewLayout.swift   | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/Chatto/Source/ChatController/Collaborators/ChatCollectionViewLayout.swift b/Chatto/Source/ChatController/Collaborators/ChatCollectionViewLayout.swift
index 64d3be417..e1c5834af 100644
--- a/Chatto/Source/ChatController/Collaborators/ChatCollectionViewLayout.swift
+++ b/Chatto/Source/ChatController/Collaborators/ChatCollectionViewLayout.swift
@@ -60,6 +60,15 @@ public struct ChatCollectionViewLayoutModel {
             calculatedForWidth: collectionViewWidth
         )
     }
+
+    public static func createEmptyModel() -> ChatCollectionViewLayoutModel {
+        return ChatCollectionViewLayoutModel(
+            contentSize: .zero,
+            layoutAttributes: [],
+            layoutAttributesBySectionAndItem: [],
+            calculatedForWidth: 0
+        )
+    }
 }
 
 open class ChatCollectionViewLayout: UICollectionViewLayout {
@@ -77,7 +86,10 @@ open class ChatCollectionViewLayout: UICollectionViewLayout {
     open override func prepare() {
         super.prepare()
         guard self.layoutNeedsUpdate else { return }
-        guard let delegate = self.delegate else { return }
+        guard let delegate = self.delegate else {
+            self.layoutModel = ChatCollectionViewLayoutModel.createEmptyModel()
+            return
+        }
         var oldLayoutModel = self.layoutModel
         self.layoutModel = delegate.chatCollectionViewLayoutModel()
         self.layoutNeedsUpdate = false