Use if instead of unless

Author: nattsw

lib/discourse_translator/guardian_extension.rb

@@ -20,7 +20,7 @@ def can_detect_language?(post)
   end
 
   def can_translate?(post)
-    return false unless user_group_allow_translate?
+    return false if !user_group_allow_translate?
 
     if SiteSetting.experimental_topic_translation
       return false if post.translation_for(I18n.locale).present?