[FIX] portal_rating: fix traceback on rating

before this commit:
when user provides feedback on chatter without selecting rating stars
it generates an error and prevents from submitting feedback.
in this commit:
changed default_rating_value to zero in order to prevent the error.
now, it is possible to provide feedback without selecting rating stars.

task-2268849
Closes https://github.com/odoo/odoo/pull/52295

closes odoo/odoo#55397

X-original-commit: dcb47d03db73b7ca8a18f50cdb14abf704e3ac52
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

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

@@ -36,7 +36,7 @@ PortalComposer.include({
         this.options = _.defaults(this.options, {
             'default_message': false,
             'default_message_id': false,
-            'default_rating_value': false,
+            'default_rating_value': 0.0,
             'force_submit_url': false,
         });
         // star input widget