multiple prefixe user/groups widget generates a bug on advanced search

Advanced Search does not retrieve any result because of the widget tied to fichier:responsable (multiple prefixe user/groups widget).

Here is a query that is generated although I did not fill anything on this widget :

2011-02-25 11:41:19,383 DEBUG [org.nuxeo.ecm.platform.query.nxql.CoreQueryDocumentPageProvider] Perform query for provider 'nxql_search': 'SELECT * FROM Document WHERE fichier:project = 'projet1' AND fichier:responsable = '[Ljava.lang.String;@3639d41' AND (ecm:mixinType != 'HiddenInNavigation' AND ecm:isCheckedInVersion = 0) ORDER BY dc:title' with pageSize=10, offset=0 ORDER BY dc:title' with pageSize=20, offset=0