Course Progress: fix error when exporting progress when no thematic where set -refs BT#21016

Author: NicoDucou

main/course_progress/thematic_controller.php

@@ -210,6 +210,10 @@ public function thematic($action)
                     $pdfOrientation = api_get_configuration_value('thematic_pdf_orientation');
 
                     $list = $thematic->get_thematic_list();
+                    if ($list === false) {
+                        header('Location: '.api_get_self().'?'.api_get_cidreq());
+                        exit;
+                    }
                     $item = [];
                     $listFinish = [];
                     foreach ($list as $theme) {

main/inc/lib/thematic.lib.php

@@ -310,6 +310,8 @@ public static function get_thematic_list(
                     $data[$row['id']] = $row;
                 }
             }
+        } else {
+            return false;
         }
 
         return $data;