(issue1794) Safeguard against layers without extent. Just create a broken layer but don't create a syntax error in a mapfile. The syntax error pulls down the whole user wms while this just creates one broken layer.

<?xml version="1.0" encoding="UTF-8" ?>
<rest-server>
    <!--  The port which the ArtifactDatabase (ArtifactServer) will bind to. -->
    <port>8181</port>
    <listen>localhost</listen>
</rest-server>