[FIX] website_slides: fix crashes on channel creation/edit

SPECIFICATIONS

Before this commit, creating a channel would crash because of NewID key
not existing in a dictionary for compute fields. A crash would also happen
when deleting a slide from the channel form view.

LINKS

Task 1978731
PR #33255

addons/website_slides/models/slide_channel.py

@@ -227,7 +227,7 @@ class Channel(models.Model):
             result[cid].update(cdata)
 
         for record in self:
-            record.update(result[record.id])
+            record.update(result.get(record.id, {}))
 
     def _compute_slides_statistics_type(self, read_group_res):
         """ Compute statistics based on all existing slide types """