ComboBox with script_path on edit [BUG]


I use in my code a dhtmlxCombo that loads data into Ajax.
Everything works well at creation but in editing I have a bug :unamused:

Here is the url of my webservice : index.php?option=com_scheduler&task=event.filterAdresse&format=xml
When I edit an event, the url becomes : index.php?option=com_scheduler&task=event.filterAdresse&format=xml?id=25411&uid=1484145915016

The 2 question marks are the cause of the problem, but how to correct this ?
Do I have to use a script without $_GET argument ?

Thanks for your help