anchor.diff:                              }
                           }
   
  -                        if (!historyResult) {
  +                        if (historyResult === null) {
                             alert("using backup method this.history[" + pref + "]");
                             historyResult = this.history[pref];
                             alert("this.history[" + pref + "] returned '" + historyResult + "'");
  
positive.code:                        alert("Error in Prefs.getString: " + err);
                      }
  
                      if (!historyResult) {
                         alert("neither <%=renderResponse.encodeURL(getHistoryUrl.toString())%> nor this.history[" + pref + "] returned a result!");
                         historyResult = "";
                      }
  
negative.code:                         alert("ajaxResult.responseText was '" + ajaxResult.responseText + "'");
                          var historyResultObj = $.parseJSON(ajaxResult.responseText);
                          alert("$.parseJSON(...) result was '" + historyResultObj + "'");
                          if (historyResultObj !== null) {
                              historyResult = historyResultObj.history;
                              if (historyResult !== null) {
                                  alert("historyResult was '" + historyResult + "'");
                              }
                              else if (historyResultObj.error !== null)
                              {
                                  alert("error was '" + historyResultObj.error + "'");
                              }
  