title: Weird Solr/Lucene behaviors with boolean operators
body: <p>I'm crashing into a weird behavior with - operators in Solr/Lucene query syntax. 
  If I execute the query </p>
  
  <pre><code>-text AND -text 
  </code></pre>
  
  <p>I get all expected results (lot), but if I put some parenthesis like </p>
  
  <pre><code>-text AND (-text) 
  </code></pre>
  
  <p>or </p>
  
  <pre><code>(-text) AND (-text) 
  </code></pre>
  
  <p>then I get no results at all. I can't understand why. 
  Do you have an explanation for this behavior? </p>
  
  <p>Thank you in advance.</p>