[FIX] website_event_track: use image_medium avatar

The default image field is usally too large for use
as a speaker avatar.
The implementation of the field should have been
a simple "related" field too, instead of a custom
computed field.

addons/website_event_track/models/event.py

@@ -53,15 +53,7 @@ class event_track(models.Model):
         ('0', 'Low'), ('1', 'Medium'),
         ('2', 'High'), ('3', 'Highest')],
         'Priority', required=True, default='1')
-    image = fields.Binary('Image', compute='_compute_image', store=True, attachment=True)
-
-    @api.one
-    @api.depends('speaker_ids.image')
-    def _compute_image(self):
-        if self.speaker_ids:
-            self.image = self.speaker_ids[0].image
-        else:
-            self.image = False
+    image = fields.Binary('Image', related='speaker_ids.image_medium', store=True, attachment=True)
 
     @api.model
     def create(self, vals):