Based on the Expression Language Component
If a field is missing from a line in the upfront data, it will default to null.
example:
['city' => 'Paris', 'country' => 'France'],
['city' => 'New-York' /* Missing country */],
// Will result in
['city' => 'Paris', 'country' => 'France'],
['city' => 'New-York' 'country' => null],No options for this component.