Impossible to create a new datasource through configuration tool if an invalid one is already created.

Steps to reproduce :

• Go to the configuration tool into the administration
• Add an invalid datasource through the configuration tool
• But don't use it
• Try to add another datasource through the configuration tool, the datasource creation widget is opened but the datatype field stay empty.

We have the following JS error :

2017-05-22T15:10:17+02:00    ERROR    [Ametys.form.ConfigurableFormPanel.FieldCheckersManager]    La vérification a échoué.<br/>Appuyez sur 'Détails' pour en savoir plus ou consultez les journaux de l'application. (Vérification globale:    Access denied for user 'smile'@'%' to database 'ideo2_v4')