[FIX] mass_mailing: unregister ResizeObserver on unmount

Steps to reproduce
==================

This only seem to happen on Firefox

- Go to Email Marketing
- Open a campaign
- Go back to the homepage by using the topleft square button

-> `$(...).offset() is undefined`

Cause of the issue
==================

The ResizeObserver used in MassMailingFullWidthViewController is still
triggered, even though it shoudln't.

Solution
========

Disconnect the observer when the component is unmounted.

opw-3271101

closes odoo/odoo#118785

X-original-commit: d5f6bc2b33c3b83520ed2ed710610b69dbe67b75
Signed-off-by: Hubert Van De Walle <huvw@odoo.com>

addons/mass_mailing/__manifest__.py

@@ -130,6 +130,7 @@
             'mass_mailing/static/src/snippets/s_showcase/options.js',
             'mass_mailing/static/src/snippets/s_rating/options.js',
             'mass_mailing/static/tests/mass_mailing_html_tests.js',
+            'mass_mailing/static/tests/mailing_mailing_view_form_tests.js',
         ],
     },
     'license': 'LGPL-3',

addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js

@@ -30,6 +30,7 @@ export class MassMailingFullWidthViewController extends formView.Controller {
         });
         onWillUnmount(() => {
             $('.o_content').off('.repositionMailingEditorSidebar');
+            this._resizeObserver.disconnect();
         });
     }
     //--------------------------------------------------------------------------

addons/mass_mailing/static/tests/mailing_mailing_view_form_tests.js

@@ -0,0 +1,71 @@
+/** @odoo-module **/
+
+import { setupViewRegistries } from "@web/../tests/views/helpers";
+import { patchWithCleanup } from "@web/../tests/helpers/utils";
+import { createWebClient, doAction } from "@web/../tests/webclient/helpers";
+import { MassMailingFullWidthViewController } from "@mass_mailing/js/mailing_mailing_view_form_full_width";
+
+let serverData;
+
+QUnit.module("mass_mailing", {}, function () {
+    QUnit.module("MassMailingFullWidthViewController", (hooks) => {
+        hooks.beforeEach(() => {
+            serverData = {
+                models: {
+                    partner: {
+                        fields: {
+                            display_name: { string: "Displayed name", type: "char" },
+                        },
+                    },
+                },
+
+                actions: {
+                    1: {
+                        id: 1,
+                        name: "test",
+                        res_model: "partner",
+                        type: "ir.actions.act_window",
+                        views: [[false, "form"]],
+                    },
+                    2: {
+                        id: 2,
+                        name: "test",
+                        res_model: "partner",
+                        type: "ir.actions.act_window",
+                        views: [[false, "list"]],
+                    },
+                },
+
+                views: {
+                    "partner,false,form": `<form js_class="mailing_mailing_view_form_full_width">
+                        <field name="display_name"/>
+                    </form>`,
+                    "partner,false,list": `<tree><field name="display_name"/></tree>`,
+                    "partner,false,search": `<search/>`,
+                },
+            };
+
+            setupViewRegistries();
+        });
+
+        QUnit.test("unregister ResizeObserver on unmount", async (assert) => {
+            patchWithCleanup(MassMailingFullWidthViewController.prototype, {
+                setup() {
+                    this._super();
+                    patchWithCleanup(this._resizeObserver, {
+                        disconnect() {
+                            assert.step("disconnect");
+                            return this._super(...arguments);
+                        },
+                    });
+                },
+            });
+
+            const webClient = await createWebClient({ serverData });
+            await doAction(webClient, 1);
+            assert.verifySteps([]);
+            await doAction(webClient, 2);
+            assert.verifySteps(["disconnect"]);
+        });
+    });
+});