title: Mongoose or operator with Date
body: <p>I am trying to write a query like:</p>
  
  <pre><code>var query = {
      userId: req.params.userId,
      isActive: true,
      'interval.start': {
          $lte: now
      },
      'interval.end': {
          $or: [
              { $gte: now },
              { $exists: false },
              { $eq: null } 
          ]
      }
  };
  </code></pre>
  
  <p>What I am trying to achieve is I want to find columns that should fit to these conditions:</p>
  
  <ul>
  <li>interval.end Date should be greater than now.</li>
  <li>OR end date shouldn't exist</li>
  <li>OR it should exist to null.</li>
  </ul>
  
  <p>I am getting: <code>Can't use $or with Date.</code> error.</p>
  
  <p>Thank you.</p>