title: Pass empty string to cucumber DataTable
body: <p>I'm updating my cucumber version from old info.cukes to latest io.cucumber (v6.8.1) and some of my tests are failing due to change of transformer behavior.
  Passing empty strings used to be possible but now they are transformed to <code>null</code>. How can I pass empty string to DataTable argument?</p>
  <pre><code>  Scenario: Testing datatable with empty string
      When Passing empty string as second parameter
        | first  | second |
        | simple |        |
  </code></pre>
  <pre class="lang-java prettyprint-override"><code>@When(&quot;Passing empty string as second parameter&quot;)
      public void test_definition(DataTable dataTable) {
          List&lt;Map&lt;String, String&gt;&gt; maps = dataTable.asMaps(String.class, String.class);
          System.out.println(maps);
  // this results in [{first=simple, second=null}]
  // is there a way to pass empty string and achieve [{first=simple, second=}]?
      }
  </code></pre>