[FIX] web: Show create button on multiEdit + unit test

What are the steps to reproduce your issue ?

    1. Install project
    2. Open any project
    3. Switch to list view and display by Stage
    4. Open categoryA and select some records
    5. Open CategoryB

What is currently happening ?

    The button create is not displayed

What are you expecting to happen ?

    Don't hide create button

opw-2423701

closes odoo/odoo#65266

X-original-commit: 813b9fc4
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>