[media] File download should retrive decoded path (#6137)

This aims to fix a bug that was experienced by a CCNA user when trying to download a file that had a '&' in the name. SQL encodes strings containing special chars and thus we need to use the decoded file names in the path when downloading files from media module.

    Resolves #6136

modules/media/ajax/FileDownload.php

@@ -24,7 +24,7 @@
 
 // Make sure that the user isn't trying to break out of the $path
 // by using a relative filename.
-$file     = basename($_GET['File']);
+$file     = html_entity_decode(basename($_GET['File']));
 $config   =& NDB_Config::singleton();
 $path     = $config->getSetting('mediaPath');
 $filePath = $path . $file;