diff --git a/main/survey/surveyUtil.class.php b/main/survey/surveyUtil.class.php
index 8d2123ef3a..3d5fa236b5 100755
--- a/main/survey/surveyUtil.class.php
+++ b/main/survey/surveyUtil.class.php
@@ -3186,14 +3186,25 @@ class SurveyUtil
             $array[2] = $survey[2].$session_img;
             $array[3] = $survey[3];
             $array[4] = $survey[4];
-            $array[5] = api_convert_and_format_date(
-                $survey[5],
-                $allowSurveyAvailabilityDatetime ? DATE_TIME_FORMAT_LONG : DATE_FORMAT_LONG
-            );
-            $array[6] = api_convert_and_format_date(
-                $survey[6],
-                $allowSurveyAvailabilityDatetime ? DATE_TIME_FORMAT_LONG : DATE_FORMAT_LONG
-            );
+
+            // Dates
+            $array[5] = '';
+
+            if (!empty($survey[5]) && $survey[5] !== '0000-00-00' && $survey[5] !== '0000-00-00 00:00:00') {
+                $array[5] = api_convert_and_format_date(
+                    $survey[5],
+                    $allowSurveyAvailabilityDatetime ? DATE_TIME_FORMAT_LONG : DATE_FORMAT_LONG
+                );
+            }
+
+            $array[6] = '';
+            if (!empty($survey[6]) && $survey[6] !== '0000-00-00' && $survey[6] !== '0000-00-00 00:00:00') {
+                $array[6] = api_convert_and_format_date(
+                    $survey[6],
+                    $allowSurveyAvailabilityDatetime ? DATE_TIME_FORMAT_LONG : DATE_FORMAT_LONG
+                );
+            }
+
             $array[7] =
                 Display::url(
                     $survey['answered'],
diff --git a/main/survey/survey_list.php b/main/survey/survey_list.php
index 92c85026ab..b9ba3255ab 100755
--- a/main/survey/survey_list.php
+++ b/main/survey/survey_list.php
@@ -23,7 +23,7 @@ $current_course_tool = TOOL_SURVEY;
 $currentUserId = api_get_user_id();
 
 api_protect_course_script(true);
-$action = isset($_GET['action']) ? Security::remove_XSS($_GET['action']) : null;
+$action = isset($_GET['action']) ? Security::remove_XSS($_GET['action']) : '';
 
 // Tracking
 Event::event_access_tool(TOOL_SURVEY);