[FIX] website_slides: prevent traceback while accessing archived embedded slide

When user archive a slide from a course and try to access route
'/slides/embed/<int:slide_id>' of that particular slide, user get the error.

steps to reproduce:
    1. Go to Website and click on courses menu.
    2. Open a course and archive a slide in it.
    3. Then go to '/slides/embed/<int:slide_id>' route.
    4. Access that particular slide that you have archived in route.
    5. The error will occur.

Applying this commit will fix this issue.

sentry-4025579653

closes odoo/odoo#120280

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

addons/website_slides/controllers/main.py

@@ -1125,6 +1125,8 @@ class WebsiteSlides(WebsiteProfile):
         # try accessing slide, and display to corresponding template
         try:
             slide = request.env['slide.slide'].browse(slide_id)
+            if not slide.active:
+                raise werkzeug.exceptions.NotFound()
             if is_embedded:
                 request.env['slide.embed'].sudo()._add_embed_url(slide.id, referrer_url)
             values = self._get_slide_detail(slide)