check for django.jQuery existence before using it

This code seems to deal with the case of django global object coming from the admin:
https://github.com/django/django/blob/1.6.5/django/contrib/admin/static/admin/js/jquery.init.js#L7

But since Django 1.6, a global django object can also exist through the use of javascript_catalog view for instance, but this time without jQuery in it:
https://github.com/django/django/blob/1.6.5/django/views/i18n.py