FIX: Can't recover a post when its user has been deleted.

https://meta.discourse.org/t/moving-posts-to-new-topic/58436

lib/guardian/post_guardian.rb

@@ -149,7 +149,11 @@ module PostGuardian
 
   # Recovery Method
   def can_recover_post?(post)
-    is_staff? || (is_my_own?(post) && post.user_deleted && !post.deleted_at)
+    if is_staff?
+      post.deleted_at && post.user
+    else
+      is_my_own?(post) && post.user_deleted && !post.deleted_at
+    end
   end
 
   def can_delete_post_action?(post_action)

lib/guardian/topic_guardian.rb

@@ -52,7 +52,7 @@ module TopicGuardian
 
   # Recovery Method
   def can_recover_topic?(topic)
-    is_staff?
+    topic && topic.deleted_at && topic.user && is_staff?
   end
 
   def can_delete_topic?(topic)