when I cxlick the Add Header Background Image(s) the screen becomes black whithout retourn. In the Styling list of the template is a bottom COM_TEMPLATES_header_slides_modal_FIELDSET_LABEL between General Styling and Menues, and there is a Bottom COM_TEMPLATES_list_templates_modal_FIELDSET_LABEL between Social Media Icons and Custum css. Both of theese bottoms do nothing. What shall I do ?