title: window.mozIndexedDB is null in Firefox 15
body: <p>I'm trying to run the "Using IndexedDB" sample code on <a href="https://developer.mozilla.org/en-US/docs/IndexedDB/Using_IndexedDB" rel="nofollow">https://developer.mozilla.org/en-US/docs/IndexedDB/Using_IndexedDB</a></p>
  
  <p>Right out of the gate I stumble with the first line of code:
  <code>window.indexedDB = window.indexedDB || window.webkitIndexedDB || window.mozIndexedDB;</code></p>
  
  <p>Using Firebug I see that <code>window.indexedDB</code> is undefined as expected for FF 15, window.webkitIndexedDB is undefined as expected (FF isn't webkit) but <code>window.mozIndexedDB</code> is null but not undefined. If it's null that tells me it exists but doesn't have a valid value/isn't initialized.</p>
  
  <p>This is with Firefox 15.0.1 on OSX 10.6.8 and Ubuntu 12.04. Can somebody tell me why I'm not able to see/use <code>window.mozIndexedDB</code>? Am I doing something wrong?</p>
  
  <p>For completeness, here's my JavaScript file:</p>
  
  <pre><code>window.indexedDB = window.indexedDB || window.webkitIndexedDB || window.mozIndexedDB;
  
  var request = window.indexedDB.open("MyTestDatabase", 3);
  var db;
  
  request.onerror = function (event) {
      alert("Oops, request.onerror");
  };
  
  request.onsuccess = function (event) {
      // Do something with request.result!
      alert("Made it to request.onsuccess");
  
      db = request.result;
  };
  
  // This event is only implemented in recent browsers
  request.onupgradeneeded = function (event) {
      alert("Made it to request.onupgradeneeded");
  };
  
  db.onerror = function (event) {
      alert("Database error (db.onerror): " + event.target.errorCode);
  };
  </code></pre>