[FIX] portal_rating: catch error when no message submitted

Steps to reproduce:
- Install e-Commerce
- Go to your portal into a quotation
- Go to the chatter and send an empty message

Issues:
A traceback is shown

Solution:
Catch the error and discard it as the parent method is already
displaying the error message to the user.

opw-3877096

closes odoo/odoo#162424

Signed-off-by: Mattis Megevand (mmeg) <mmeg@odoo.com>

addons/portal_rating/static/src/js/portal_composer.js

@@ -149,7 +149,7 @@ PortalComposer.include({
               this.trigger_up('reload_rating_popup_composer', result);
             });
             $modal.modal('hide');
-        });
+        }, () => {});
     },
 
     /**