Allow passing null in twig_is_selected_choice
Allow passing null in twig_is_selected_choice

In the cached file of my application I can see the following code fragment that have been generated by Symfony:
```php
if (( !((array_key_exists("render_preferred_choices", $context)) ? (_twig_default_filter((isset($context["render_preferred_choices"]) || array_key_exists("render_preferred_choices", $context) ? $context["render_preferred_choices"] : (function () { throw new RuntimeError('Variable "render_preferred_choices" does not exist.', 88, $this->source); })()), false)) : (false)) && Symfony\Bridge\Twig\Extension\twig_is_selected_choice($context["choice"], (isset($context["value"]) || array_key_exists("value", $context) ? $context["value"] : (function () { throw new RuntimeError('Variable "value" does not exist.', 88, $this->source); })())))) {
                    echo " selected=\"selected\"";
                }
```

The 2nd Arg passed when calling ``twig_is_selected_choice`` if the result of ``(isset($context["value"]) || array_key_exists("value", $context) ? $context["value"]``.

In that condition, if ``$context['value'] = null, we pass the null

Currently I got the following error:
```
Symfony\Bridge\Twig\Extension\twig_is_selected_choice(): Argument #2 ($selectedValue) must be of type array|string, null given, called in X:\workspace-novento\novento-vip-lounge\var\cache\admin_dev\twig\01\01615438ee40292438687b29025d08a9.php on line 534
```
symfony/twig-bridge