Fixed issue #10052: 0 as answer code in radio list causes problems wh…

…en 'No answer' is enabled

Dev: Replaces (!$var) with !isset($var) to cope with situations where $var = 0
Dev: Fix only for radio list HTML rendering. Similar issues may exist for other question types

application/helpers/qanda_helper.php

@@ -1789,7 +1789,7 @@ function do_list_radio($ia)
 
     if ($ia[6] != 'Y' && SHOW_NO_ANSWER == 1)
     {
-        if ((!$_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] || $_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == '') || ($_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == ' ' ))
+        if ((!isset($_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]]) || $_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == '') || ($_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == ' ' ))
         {
             $check_ans = CHECKED; //Check the "no answer" radio button if there is no answer in session.
         }
@@ -1893,7 +1893,7 @@ function do_listwithcomment($ia)
 
         if ($ia[6] != 'Y' && SHOW_NO_ANSWER == 1)
         {
-            if ((!$_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] || $_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == '') ||($_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == ' ' ))
+            if ((!isset($_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]]) || $_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == '') ||($_SESSION['survey_'.Yii::app()->getConfig('surveyID')][$ia[1]] == ' ' ))
             {
                 $check_ans = CHECKED;
             }