[FIX] mail: no crash when click on failure in mobile

Before this commit, when clicking on a mail failure in
the messaging menu in mobile, it crashed.

`NotificationGroupView` is already destroyed, so it crashed
due to attempting to access a field (`messaging`)

Task-3013202

closes odoo/odoo#102986

X-original-commit: 73b94715f0d0086d361937491c27c611a03a9f67
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/models/notification_group_view.js

@@ -19,9 +19,10 @@ registerModel({
                 // handled in `_onClickMarkAsRead`
                 return;
             }
+            const messaging = this.messaging;
             this.notificationGroup.openDocuments();
-            if (!this.messaging.device.isSmall) {
-                this.messaging.messagingMenu.close();
+            if (!messaging.device.isSmall) {
+                messaging.messagingMenu.close();
             }
         },
         /**