* ext/tk/lib/tk/menuspec.rb: commit miss on my last commitment.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24097 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/tk/lib/tk/menuspec.rb

@@ -279,7 +279,7 @@ module TkMenuSpec
       end
     end
 
-    keys = default_opts.dup
+    keys = (default_opts)? default_opts.dup: {}
 
     tearoff = keys.delete('tearoff') if keys.key?('tearoff')
     tearoff = false unless tearoff # nil --> false