When using fillin filter, after validation success (all form fields are ok) if you want display page without form, fillin filter is still enabled and throws exception "Exception - No form found in this page". Use this snippet to prevent it.

in sfFillInFormFilter.class.php file

  public function execute($filterChain)
  {
    // execute next filter
    $filterChain->execute();
 
    $context  = $this->getContext();
    $response = $context->getResponse();
    $request  = $context->getRequest();
 
    // add these two lines
    if(! $request->hasErrors())
        return;