title: How to OR null values in Solr query with a range
body: <p>I have a query where <code>fq=score_dx:[0.0 TO 1]</code></p>
  
  <p>We need something like <code>score_dx:[0.0 TO 1] OR score_dx:''</code></p>
  
  <p>This is not working. How to do <code>OR null</code> with the existing <code>fq</code>?</p>