title: Json Cpp isMember() Returns True always
body: <p>For example in a simple json</p>
  
  <pre><code>{
      "A" :
      {
         "B" :
         {
           --something--
         }
      }
  }
  </code></pre>
  
  <h2>First Case:</h2>
  
  <pre><code>json::Value root;
  const Json::Value x = root["A"]["B"];
  if (root.isMember("A")) --- always returns TRUE..
  </code></pre>
  
  <h2>Second Case:</h2>
  
  <pre><code>Json::Value root;
  If (root.isMember("A"))  ---- works fine
  const Json::Value x = root["A"]["B"]; 
  </code></pre>
  
  <p>Any idea what's wrong with First Case? even if I get <code>x</code> before <code>isMember()</code> call.</p>