fix primary_key (an old bug that still exist here)

xfynx · xfynx · commit 5840fe930e22 · 2018-03-06T18:07:04.000+05:00
diff --git a/lib/active_admin/mongoid/document.rb b/lib/active_admin/mongoid/document.rb
@@ -39,7 +39,7 @@ class << self
       end
     end
 
-    self.primary_key ||= [:_id]
+    self.primary_key ||= :_id
   end
 
   module ClassMethods
