title: Filtering objects with null property on Realm for React Native
body: <p>React Native and Realm noob here!</p>
  
  <p>I want to load objects where one particular property is null.</p>
  
  <p>I tried to filter them like this:</p>
  
  <pre><code>let goals = Modal.objects('goal').filtered('SubGoalOf == $0', null);
  </code></pre>
  
  <p>I've also tried this:</p>
  
  <pre><code>let goals = Modal.objects('goal').filtered('SubGoalOf == $0', {});
  </code></pre>
  
  <p>But got errors like "Value is not an object" and "object is not Realm Object". Query without filtered method is working perfectly and returning everything. But that's not exactly what I am going for.</p>
  
  <p>This would be the schema:</p>
  
  <pre><code>Goal.schema = {
    name: 'goal',
    primaryKey: 'id',
    properties: {
      id: 'string',
      createdOn: 'date',
      itemName: {type: 'string', indexed: true },
      SubGoalOf: {type: 'goal', optional: true},
      ShouldNotify: 'bool',
      WhenNotify: {type:'date', optional: true},
      deadline: {type:'date', optional: true},
      isComplete: 'bool',
      completedOn: {type:'date', optional: true},
    }
  }
  </code></pre>
  
  <p>It would be great, if anyone could help me. Thank you.</p>