Allow sysops to delete invites

sections/user/delete_invite.php

 $DB->query("
   SELECT InviterID
   FROM invites
-  WHERE InviteKey = '$InviteKey'");
+  WHERE InviteKey = ?", $InviteKey);
 list($UserID) = $DB->next_record();
-if (!$DB->has_results() || $UserID != $LoggedUser['ID']) {
+if (!$DB->has_results()) {
   error(404);
 }
+if ($UserID != $LoggedUser['ID'] && $LoggedUser['PermissionID'] != SYSOP) {
+  error(403);
+}
 
 $DB->query("
   DELETE FROM invites
-  WHERE InviteKey = '$InviteKey'");
+  WHERE InviteKey = ?", $InviteKey);
 
 if (!check_perms('site_send_unlimited_invites')) {
   $DB->query("
     SELECT Invites
     FROM users_main
-    WHERE ID = $UserID
-    LIMIT 1");
+    WHERE ID = ?
+    LIMIT 1", $UserID);
   list($Invites) = $DB->next_record();
   if ($Invites < 10) {
     $DB->query("
       UPDATE users_main
       SET Invites = Invites + 1
-      WHERE ID = '$UserID'");
+      WHERE ID = ?", $UserID);
     $Cache->begin_transaction("user_info_heavy_$UserID");
-    $Cache->update_row(false, array('Invites' => '+1'));
+    $Cache->update_row(false, ['Invites' => '+1']);
     $Cache->commit_transaction(0);
   }
 }