How can I make a variable in the constructor make it optional (flutter)?

please help me solve the following problem.
This part of my code:

class MeditationCard extends StatelessWidget {
  const MeditationCard({
    required this.title,
    required this.image,
    this.route});

final String title;
final String image;
final String route;
...

I need the route variable as optional, but when I remove the flag, I get an error and ask me to make the variable mandatory.
Tried different approaches but didn’t work for me
This alert dialog

The parameter ‘route’ can’t have a value of ‘null’ because of its
type, but the implicit default value is ‘null’.

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>Solution :

This happened because of null safety check.In order to set nullable variable, you should use ?, try this:

final String? route;