PHP8 Compatibility count

Problem/Motivation

This issue appears with the new version of PHP 8 and the way that handles the count parameters.

The official documentation doesn't highlight the difference between versions:
https://www.php.net/manual/es/function.count.php

More info:
https://runebook.dev/en/docs/php/function.count

Identified points:
- Count in tmgmt_cdt/src/TmgmtCdtTranslatorUi.php line 838

Steps to reproduce

On real mode activated:

1. Add any item to the cart
2. Submit the item

Proposed resolution

Add checks before the count.

Remaining tasks

User interface changes

API changes

Data model changes