Enable "null" TableNode/PyStringNode parameters

We are using some tests when we allow the null TableNode or PyStringNode . Eg:

test.feature
Then I should get an email on "test1@mail.com"
#...
Then I should get an email on "test2@mail.com" with:
 """
 This is a test mail!
 """

FeatureContext.php
/** @Then /^I should get an email on "(?P<email>[^"]+)"(?:| with:)$/ */
public function iShouldGetAnEmail($email, PyStringNode $text = null)
{
    //...
    if ($text) {
        // Check the content also if it is set
    }
}