title: Transform empty list to empty string in jolt
body: <p>The use case is sometimes I will get an empty list as the input and instead of getting null as output for some specs, I want either empty string or no output instead of null.</p>
  <p>And if the input is not an empty list, I want the spec to transform the input and give the results.</p>
  <p>Input:</p>
  <pre><code>[]
  </code></pre>
  <p>Specs:</p>
  <pre><code>[{
      &quot;operation&quot;: &quot;modify-overwrite-beta&quot;,
      &quot;spec&quot;: {
        &quot;*&quot;: {
          &quot;comments&quot;: &quot;Sample values.&quot;
        }
      }
  },
  
    {
      &quot;operation&quot;: &quot;shift&quot;,
      &quot;spec&quot;: {
        &quot;*&quot;: {
          &quot;a&quot;: &quot;[&amp;1].A&quot;,
          &quot;b&quot;: &quot;[&amp;1].B&quot;,
          &quot;c&quot;: &quot;[&amp;1].C&quot;,
          &quot;comments&quot;: &quot;[&amp;1].comments&quot;
        }
      }
    }
  ]
  </code></pre>
  <p>desired output:</p>
  <pre><code>
  </code></pre>
  <p>Output received:</p>
  <pre><code>null
  </code></pre>
  <p>Is there a way to get nothing in the output if the input is empty list?</p>