Must use proper internal API params now that it has changed

Author: enebo

lib/ruby/stdlib/jruby/synchronized.rb

@@ -15,10 +15,10 @@ def self.append_features(cls)
 
     def self.extend_object(obj)
       obj_r = JRuby.reference0(obj)
-      singleton_class = obj_r.singleton_class
+      singleton_class = obj_r.singleton_class(obj_r.runtime.current_context)
       JRuby.reference(singleton_class).become_synchronized
 
       super
     end
   end
-end
+end