Index: theme.php
===================================================================
--- theme.php	(revision 19286)
+++ theme.php	(working copy)
@@ -496,7 +496,7 @@
 function get_theme($theme) {
 	$themes = get_themes();
 
-	if ( array_key_exists($theme, $themes) )
+	if ( is_array( $themes ) && array_key_exists($theme, $themes) )
 		return $themes[$theme];
 
 	return null;