I do have only SoapUI Open Source edition of specific version and that does not have a separate field for password as shown below.
In this case, credentials can be part of Connection String itself. such as:
jdbc:postgresql:dbserver:5432:ProductDB&user=root&password=secret
May be you can try including the password in the connection string and leave Password blank to see if that helps.
Of course, use parameterized values for each of the above in the connection string, assign below string to JDBC_CONNECTION_STRING project property and use it in JDBC Step's connection string and see what happens, leave password blank
jdbc:postgresql:${#Project#DB_HOST}:${#Project#DB_PORT}:${#Project#DB_NAME}&user=${#Project#DB_USER}&password=${#Project#DB_PASSWORD}
