Require nullsafe operator


`<rule ref="SlevomatCodingStandard.ControlStructures.RequireNullSafeObjectOperator" />`

Fixable.

Error message: `Operator ?-> is required.`

Resolves:

```php
if ($item === NULL || $item->date === NULL) {
```

To

```php
if ($item?->date === NULL) {
```