title: null plus null is sometimes 0, sometimes "nullnull"
body: <p>In compiled mode.</p>
  
  <pre><code>String s1 = null;
  String s2 = null;
  s2 = s1 + s2;
  Window.alert("null + null = " + s2);
  </code></pre>
  
  <p>result:</p>
  
  <pre><code>"null + null = nullnull"
  </code></pre>
  
  <p>But this piece of code:</p>
  
  <pre><code>public String getValue(DocListsInfo object) {
      String s1 = object.getUrlForApplication();
      Window.alert("2: " + s1);
      String s2 = object.getEodLink();
      Window.alert("3: " + s2);
      String s3 = s1 + s2;
      Window.alert("4: " + s3);
      return s3;
  }
  
  =&gt;
  // compiled javascript:
  function NUb(a){var b,c,d;b=a.q;$wnd.alert('2: '+b);c=a.g;$wnd.alert('3: '+c);d=b+c;$wnd.alert('4: '+d);return d}
  </code></pre>
  
  <p>returns 0 if both getters return null.</p>