[upgrade] db_last_error should be globalwhen used :P

other/upgrade.php

@@ -2170,6 +2170,8 @@ function changeSettings($config_vars)
 }
 function updateLastError() 
 {
+	global $db_last_error;
+
 	// clear out the db_last_error file
 	file_put_contents(dirname(__FILE__) . '/db_last_error.php', "<?php\n$db_last_error = 0;\n?" . ">\n");
 }