render does not reject when rendering fails

I would have expected this test to pass, but it fails with "expected not to get here" in addition to an out-of-band qunit failure for the actual `Compiler Error: not-a-component is not a helper`.

```js
test('render can throw', async function(assert) {
try {
await render(hbs`{{not-a-component x="y"}}`);
} catch (err) {
assert.ok(/not-a-component is not a helper/.test(err.message), "expected to see failure");
}
throw new Error("expected not to get here");
});

```