StringListConverter converts an empty String to a one element List instead of an empty List

Then string is ''

@Then("string is '$params'")
public void empty(List<String> params) {
    ensureThat(params.isEmpty(), equalTo(true));
}

Scenario: <Guess> marks as <Mark>
    Given the secret r,g,y,b
    When I guess [Guess]
    Then I should get [Mark]

  Examples:
    |Guess|Mark|
    |c,c,c,c||
    |b,c,c,c|m|