FIX: Allow user to be deleted (#236)

There is a bug now where the post's user may not always be available, causing can_translate? to throw an error.

Author: nattsw

lib/discourse_translator/guardian_extension.rb

@@ -22,7 +22,7 @@ def can_detect_language?(post)
   end
 
   def can_translate?(post)
-    return false if post.user.bot?
+    return false if post.user&.bot?
     return false if !user_group_allow_translate?
     return false if post.locale_matches?(I18n.locale)
 

spec/lib/guardian_extension_spec.rb

@@ -244,5 +244,11 @@
         end
       end
     end
+
+    it "does not error out when post user is deleted" do
+      post.update(user: nil)
+
+      expect { guardian.can_translate?(post) }.not_to raise_error
+    end
   end
 end