Additional fix for many association association script (bug in SonataMedia Gallery)

Similar to @zeliard91's fix in [pull request #209](https://github.com/sonata-project/SonataDoctrineORMAdminBundle/pull/209). This corrects an issue where clicking "tabs" at the top of the media modal window would result in a page load instead of updating the modal's html. 

![screen-shot-2013-04-30-at-12 13 14-pm](https://f.cloud.github.com/assets/199645/444999/506fa5b2-b1b1-11e2-9d13-d9356078a600.jpg)

This is related to sonata-project/SonataDoctrineORMAdminBundle#191 and sonata-project/SonataAdminBundle#1267.