Index: wp-admin/includes/media.php
===================================================================
--- wp-admin/includes/media.php	(revision 22599)
+++ wp-admin/includes/media.php	(working copy)
@@ -1377,7 +1377,8 @@
  * @since 2.5.0
  */
 function media_upload_header() {
-	echo '<script type="text/javascript">post_id = ' . intval( $_REQUEST['post_id'] ) . ";</script>\n";
+	$post_id = isset($_REQUEST['post_id']) ? intval($_REQUEST['post_id']) : 0;
+	echo '<script type="text/javascript">post_id = ' . $post_id . ";</script>\n";
 	if ( empty( $_GET['chromeless'] ) ) {
 		echo '<div id="media-upload-header">';
 		the_media_upload_tabs();
@@ -1596,7 +1597,7 @@
 
 	media_upload_header();
 
-	$post_id = intval($_REQUEST['post_id']);
+	$post_id = isset($_REQUEST['post_id']) ? intval($_REQUEST['post_id']) : 0;
 
 	$form_action_url = admin_url("media-upload.php?type=$type&tab=type&post_id=$post_id");
 	$form_action_url = apply_filters('media_upload_form_url', $form_action_url, $type);
@@ -1871,7 +1872,7 @@
 
 	media_upload_header();
 
-	$post_id = intval($_REQUEST['post_id']);
+	$post_id = isset($_REQUEST['post_id']) ? intval($_REQUEST['post_id']) : 0;
 
 	$form_action_url = admin_url("media-upload.php?type=$type&tab=library&post_id=$post_id");
 	$form_action_url = apply_filters('media_upload_form_url', $form_action_url, $type);