Problem with page_title in application.php

$params[$hash]->def('page_title', $title);

This causes a bug in the view form, causing the messages do not show the variable $head.

Example:

if (empty($this->item->id))
{
	$head = JText::_('COM_COMPONENT_FORM_SUBMIT_ITEM');
}
else
{
	$head = JText::_('COM_COMPONENT_FORM_EDIT_ITEM');
}

$title = $this->params->def('page_title', $head);