incompatible with PHP8: TypeError: count(): Argument #1 ($value) must be of type Countable|array, null given

**Problem**
Using PHP8, both simulation and execution of the deletion process lead to ``TypeError: count(): Argument #1 ($value) must be of type Countable|array, null given``

**Solution**
In order to run with PHP8, arguments of array functions ``count()`` and ``array_filter()`` need to be casted to arrays.