topics: Restrict delete and disable on default topic

include/class.topic.php

@@ -198,6 +198,10 @@ class Topic {
     }
 
     function delete() {
+        global $cfg;
+
+        if ($this->getId() == $cfg->getDefaultTopicId())
+            return false;
 
         $sql='DELETE FROM '.TOPIC_TABLE.' WHERE topic_id='.db_input($this->getId()).' LIMIT 1';
         if(db_query($sql) && ($num=db_affected_rows())) {

scp/helptopics.php

@@ -68,7 +68,8 @@ if($_POST){
                         break;
                     case 'disable':
                         $sql='UPDATE '.TOPIC_TABLE.' SET isactive=0 '
-                            .' WHERE topic_id IN ('.implode(',', db_input($_POST['ids'])).')';
+                            .' WHERE topic_id IN ('.implode(',', db_input($_POST['ids'])).')'
+                            .' AND topic_id <> '.db_input($cfg->getDefaultTopicId());
                         if(db_query($sql) && ($num=db_affected_rows())) {
                             if($num==$count)
                                 $msg = 'Selected help topics disabled';