[FIX] {im,website}_livechat: only send guest token when available

Before this commit, live chat would fail for guest portal. In this
scenario, there is no guest token. Before this commit, the guest
token was sent anyway with `null` as value which caused a crash.

closes odoo/odoo#139585

Signed-off-by: Matthieu Stockbauer (tsm) <tsm@odoo.com>

addons/im_livechat/static/src/embed/common/livechat_service.js

@@ -225,10 +225,12 @@ export class LivechatService {
     }
 
     async initializePersistedSession() {
-        await this.busService.updateContext({
-            ...this.busService.context,
-            guest_token: this.guestToken,
-        });
+        if (this.guestToken) {
+            await this.busService.updateContext({
+                ...this.busService.context,
+                guest_token: this.guestToken,
+            });
+        }
         if (this.busService.isActive) {
             this.busService.forceUpdateChannels();
         } else {

addons/website_livechat/static/tests/tours/website_livechat_as_portal.js

@@ -0,0 +1,29 @@
+/* @odoo-module */
+
+import { registry } from "@web/core/registry";
+
+registry.category("web_tour.tours").add("website_livechat_as_portal_tour", {
+    test: true,
+    shadow_dom: ".o-livechat-root",
+    steps: () => [
+        {
+            trigger: ".o-livechat-LivechatButton",
+        },
+        {
+            trigger: ".o-mail-Composer-input",
+            run: "text Hello, I need help!",
+        },
+        {
+            trigger: ".o-mail-Composer-input",
+            run() {
+                this.$anchor[0].dispatchEvent(
+                    new KeyboardEvent("keydown", { key: "Enter", which: 13, bubbles: true })
+                );
+            },
+        },
+        {
+            trigger: ".o-mail-Message:contains('Hello, I need help!')",
+            isCheck: true,
+        },
+    ],
+});

addons/website_livechat/tests/test_livechat_basic_flow.py

@@ -5,6 +5,7 @@ import datetime
 
 from odoo import tests, _
 from odoo.addons.website_livechat.tests.common import TestLivechatCommon
+from odoo.tests.common import new_test_user
 
 
 @tests.tagged('post_install', '-at_install')
@@ -140,3 +141,7 @@ class TestLivechatBasicFlowHttpCase(tests.HttpCase, TestLivechatCommon):
         self.assertEqual(channel.livechat_active, True, "The livechat session must be active as the visitor did not left the conversation yet.")
 
         return channel
+
+    def test_livechat_as_portal_user(self):
+        new_test_user(self.env, login="portal_user", groups="base.group_portal")
+        self.start_tour("/my", "website_livechat_as_portal_tour", login="portal_user")