Invalid namespace in "Parameter #X $param of function X expects callable()"

```
Parameter #2 $function_to_add of function add_action expects callable(): mixed, 'F4\\Hooks::add…' given.
```

While the namespace is really `F4\MT\Core`

```php
namespace F4\MT\Core;

class Hooks {

    public static function init() {
        add_action('customize_controls_print_scripts', __NAMESPACE__ . '\\Hooks::add_custom_js');
```

