mod_sasl2_fast: Improve handling when SASL profile unexpectedly lacks CB
This fixes a traceback reported by riau, but likely does not solve the
underlying cause, whatever that is.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Stats</title>
</head>
<body>
<h1>Glorious statistics!</h1>
<script>
var evtSource = new EventSource("/stats_stream");
evtSource.addEventListener("stats-full", function(e) {
var initial_stats = JSON.parse(e.data);
console.log(initial_stats);
}, false);
evtSource.addEventListener("stats-updated", function(e) {
var updated_stats = JSON.parse(e.data);
console.log(updated_stats);
}, false);
</script>
</body>
</html>