[FIX] mail: handle error while click on follow button

When a user click on the 'Follow' button in the chatterbox of the project
Task form view without adding any data, then traceback will appear.

Steps to reproduce(i.e Project):

- Install project module.
- Go to Project >> Tasks >> My task(you can also choose the all task menu) .
- In the list view of project.task model, click on the new button.
- In-form view of project.task model, Click on Follow Button in the chatterbox.

Error: traceback appears: "psycopg2.errors.UndefinedFunction: operator does
not exist: integer = boolean"

sentry-4243265676

closes odoo/odoo#126749

X-original-commit: eeaee0d57effb50d3a0edad1672e17bffea11d0a
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/core/web/chatter.js

@@ -280,13 +280,28 @@ export class Chatter extends Component {
         document.body.click(); // hack to close dropdown
     }
 
-    async onClickFollow() {
-        await this.orm.call(this.props.threadModel, "message_subscribe", [[this.props.threadId]], {
+    async _follow(threadModel, threadId) {
+        await this.orm.call(threadModel, "message_subscribe", [[threadId]], {
             partner_ids: [this.store.self.id],
         });
         this.onFollowerChanged();
     }
 
+    async onClickFollow() {
+        if (this.props.threadId) {
+            this._follow(this.props.threadModel, this.props.threadId);
+        } else {
+            this.onNextUpdate = (nextProps) => {
+                if (nextProps.threadId) {
+                    this._follow(nextProps.threadModel, nextProps.threadId);
+                } else {
+                    return true;
+                }
+            };
+            await this.props.saveRecord?.();
+        }
+    }
+
     /**
      * @param {MouseEvent} ev
      * @param {import("@mail/core/common/follower_model").Follower} follower

addons/mail/static/tests/web/follow_button_tests.js

@@ -57,6 +57,27 @@ QUnit.test('click on "follow" button', async (assert) => {
     assert.containsOnce($, "button:contains(Following)");
 });
 
+QUnit.test('Click on "follow" button should save draft record', async (assert) => {
+    const views = {
+        "res.partner,false,form": `
+            <form string="Partners">
+                <sheet>
+                    <field name="name" required="1"/>
+                </sheet>
+                <div class="oe_chatter">
+                    <field name="message_follower_ids"/>
+                </div>
+            </form>`,
+    };
+    const { openFormView } = await start({ serverData: { views } });
+    await openFormView("res.partner");
+    assert.containsOnce($, "button:contains(Follow)");
+    assert.containsOnce($, "div.o_field_char");
+
+    await click("button:contains(Follow)");
+    assert.containsOnce($, "div.o_field_invalid");
+});
+
 QUnit.test('click on "unfollow" button', async (assert) => {
     const pyEnv = await startServer();
     const threadId = pyEnv["res.partner"].create({});