Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 21778)
+++ wp-includes/post.php	(working copy)
@@ -4049,10 +4049,10 @@
  * @return string|bool
  */
 function wp_mime_type_icon( $mime = 0 ) {
+	$post_id = 0;
 	if ( !is_numeric($mime) )
 		$icon = wp_cache_get("mime_type_icon_$mime");
 	if ( empty($icon) ) {
-		$post_id = 0;
 		$post_mimes = array();
 		if ( is_numeric($mime) ) {
 			$mime = (int) $mime;