Thrown strings caught via onerror are sent as "undefined"

[benvinegar]

This means that such an error is not caught via our async instrumentation setTimeout, XMLHttpRequest handlers, etc, but caught via our last-resort onerror handler.

To reproduce:

<script>
// before setTimeout is instrumented by Raven.js
setTimeout(function () {
  throw 'lol'; // this will fire after Raven is configured/installed
});
</script>
<script src="https://cdn.ravenjs.com/3.11.0/raven.js"></script>
<script>
Raven.config('your-dsn').install();
</script>

This is particularly a problem for uBlock users on Safari, because that extension is triggering this error for every blocked URL.

[benvinegar]

Refs gorhill/uBlock#2415 el1t/uBlock-Safari#30