Why are wrapper menu links creating errors?

A regression was introduced in Joomla 1.6.1 that breaks all wrapper menu links.

This is fixed with the patch available here: Issue 25238

To fix manually you need to change $this->params->get to $params->get in 4 locations.

Index: components/com_wrapper/views/wrapper/view.html.php
===================================================================
--- components/com_wrapper/views/wrapper/view.html.php	(revision 20922)
+++ components/com_wrapper/views/wrapper/view.html.php	(working copy)
@@ -38,15 +38,15 @@
 			$title = JText::sprintf('JPAGETITLE', $app->getCfg('sitename'), $title);
 		}
 		$this->document->setTitle($title);

-		if ($this->params->get('menu-meta_description'))
+		if ($params->get('menu-meta_description'))
 		{
-			$this->document->setDescription($this->params->get('menu-meta_description'));
+			$this->document->setDescription($params->get('menu-meta_description'));
 		}
 
-		if ($this->params->get('menu-meta_keywords')) 
+		if ($params->get('menu-meta_keywords')) 
 		{
-			$this->document->setMetadata('keywords', $this->params->get('menu-meta_keywords'));
+			$this->document->setMetadata('keywords', $params->get('menu-meta_keywords'));
 		}
 
 		$wrapper = new stdClass();