[FIX] website_slides: leave course

Currently there is a traceback when trying to leave a course (unsubscribe)
from the frontend on the homepage of a specific course. (when clicking on
"You're enrolled")
This fixes the traceback.

closes odoo/odoo#37384

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/website_slides/controllers/main.py

@@ -513,7 +513,7 @@ class WebsiteSlides(WebsiteProfile):
 
     @http.route(['/slides/channel/leave'], type='json', auth='user', website=True)
     def slide_channel_leave(self, channel_id):
-        request.env['slide.channel'].browse(channel_id)._remove_membership(request.env.user.partner_id)
+        request.env['slide.channel'].browse(channel_id)._remove_membership(request.env.user.partner_id.ids)
         return True
 
     @http.route(['/slides/channel/tag/search_read'], type='json', auth='user', methods=['POST'], website=True)