Merge pull request #2624 from RocketChat/bug/user_loses_roles

[FIX] User is loosing roles on mapping lastMessage

Author: rafaelks

Rocket.Chat/Models/Mapping/SubscriptionModelMapping.swift

@@ -135,9 +135,18 @@ extension Subscription: ModelMappeable {
         }
 
         if values["lastMessage"].dictionary != nil {
-            let user = User()
-            user.map(values["lastMessage"]["u"], realm: realm)
-            realm?.add(user, update: true)
+            if let userIdentifier = values["lastMessage"]["u"]["_id"].string {
+                if let realm = realm {
+                    if let user = realm.object(ofType: User.self, forPrimaryKey: userIdentifier as AnyObject) {
+                        user.map(values["u"], realm: realm)
+                        realm.add(user, update: true)
+                    } else {
+                        let user = User()
+                        user.map(values["u"], realm: realm)
+                        realm.add(user, update: true)
+                    }
+                }
+            }
 
             let message = Message()
             message.map(values["lastMessage"], realm: realm)