NPE fix in AsyncHttpResponseHandler for onFailure method

Author: lvitti

library/src/com/loopj/android/http/AsyncHttpResponseHandler.java

@@ -291,9 +291,8 @@ public void onFailure(int statusCode, Header[] headers, Throwable error, String
      * @param error        the underlying cause of the failure
      */
     public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) {
-        String response;
         try {
-            response = new String(responseBody, getCharset());
+            String response = responseBody == null ? null : new String(responseBody, getCharset());
             onFailure(statusCode, headers, error, response);
         } catch (UnsupportedEncodingException e) {
             Log.e(LOG_TAG, e.toString());