Power BI Paginated and PostgreSQL: How do i get all data if parameter is blank?

I'm using a PostgreSQL ODBC data source in an Power BI Paginated report.

I have a text box parameter and it can be blank and if it's blank i want to bring all data like that parameter not exist but if text box has value then i want to filter my query with that value. How can i do that?

My query example;

`SELECT Column1 FROM MyTable WHERE Column1 in (case when ?='' then Column1 else ? end)

I tried this code but this is not working.