Index: dashboard.php
===================================================================
--- dashboard.php	(revision 20368)
+++ dashboard.php	(working copy)
@@ -364,7 +364,7 @@
 
 	echo "\n\t<p>";
 
-	if ( $theme->errors() ) {
+	if ( !$theme || $theme->errors() ) {
 		if ( ! is_multisite() || is_super_admin() )
 			echo '<span class="error-message">' . __('ERROR: The themes directory is either empty or doesn&#8217;t exist. Please check your installation.') . '</span>';
 	} elseif ( ! empty($wp_registered_sidebars) ) {