[FIX] pos_hr: initialize employeeBuffer before super call to avoid error

Steps to reproduce:
===================
- Enable Login with Employee in POS settings
- Open POS and log in with employee
- Turn off the internet connection
- Reload the POS page

Issue:
======
- POS crashes with the following error:
TypeError: Cannot read properties of undefined (reading push)
- At that point, employeeBuffer is still undefined

Cause:
======
- The method set_cashier() is triggered during the parent setup()
- employeeBuffer was only initialized after super.setup()
- In offline mode, this sequence still executes, leading to an exception
when trying to .push() into an undefined buffer

Fix:
====
- Moved the initialization of employeeBuffer to the beginning of the
setup() method

Task: 4850543
Runbot Error: 227777

closes odoo#216843

Signed-off-by: David Monnom (moda) <moda@odoo.com>

Author: abhk-odoo

addons/pos_hr/static/src/overrides/models/pos_store.js

@@ -4,14 +4,14 @@ import { browser } from "@web/core/browser/browser";
 
 patch(PosStore.prototype, {
     async setup() {
+        this.employeeBuffer = [];
         await super.setup(...arguments);
         if (this.config.module_pos_hr) {
             this.login = Boolean(odoo.from_backend) && !this.config.module_pos_hr;
             if (!this.hasLoggedIn) {
                 this.showScreen("LoginScreen");
             }
         }
-        this.employeeBuffer = [];
         browser.addEventListener("online", () => {
             this.employeeBuffer.forEach((employee) =>
                 this.data.write("pos.session", [this.config.current_session_id.id], {