Undefined index 0 when unsetting the first of two messages

Problem/Motivation

If there are two messages (and only two) and the first one is unsetted (with disable_messages module, or by custom code, it's indifferent) the following code will be executed,

$output .= filter_xss_admin($messages[0]);

resuting in an "undefined index" error, because there's no item with key 0

Proposed resolution

I propose to substitute $messages[0] with reset($messages) to have the first value regardless of the key