[FIX] bus: restore current partner in pyEnv

Since [1], `pyEnv.currentPartner` has been removed. This was
a mistake since this information is still used during tests.

This PR restores it.

[1]: https://github.com/odoo/odoo/pull/98374

closes odoo/odoo#103544

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

addons/bus/static/tests/helpers/mock_python_environment.js

@@ -104,6 +104,12 @@ let pyEnv;
     }
     pyEnv = new Proxy(
         {
+            get currentPartner() {
+                if ('res.partner' in this.mockServer.models) {
+                    return this.mockServer.getRecords('res.partner', [['id', '=', this.currentPartnerId]])[0];
+                }
+                return undefined;
+            },
             getData() {
                 return this.mockServer.models;
             },