Remove Werkzeug bug workaround from flask/app.py

According to the note in the comment, you had to check to make sure that the
defaults were not an empty dictionary because of a bug in Werkzeug pre-0.7.

Since Flask officially requires 0.7 or greater, we can remove this little
workaround.

flask/app.py

@@ -968,11 +968,6 @@ class Flask(_PackageBoundObject):
         # Add the required methods now.
         methods |= required_methods
 
-        # due to a werkzeug bug we need to make sure that the defaults are
-        # None if they are an empty dictionary.  This should not be necessary
-        # with Werkzeug 0.7
-        options['defaults'] = options.get('defaults') or None
-
         rule = self.url_rule_class(rule, methods=methods, **options)
         rule.provide_automatic_options = provide_automatic_options