Index: wp-includes/user.php
===================================================================
--- wp-includes/user.php	(revision 17521)
+++ wp-includes/user.php	(working copy)
@@ -1548,8 +1548,13 @@
 	// First, get all of the original fields
 	$user = get_userdata($ID);
 
-	// Escape data pulled from DB.
-	$user = add_magic_quotes(get_object_vars($user));
+	if( false === $user ) {
+		// No userdata was found
+		$user = array();
+	} else {
+		// Escape data pulled from DB.
+		$user = add_magic_quotes(get_object_vars($user));
+	}
 
 	// If password is changing, hash it now.
 	if ( ! empty($userdata['user_pass']) ) {