Update uglify
[Fix] Ensure that error, thrown callbacks chain.

Previously, there were two bugs:

1. The thrown and error callbacks didn't return the values returned by
the callbacks passed into them. They swallowed the return values.
2. Thrown errors would end up overwriting rejected errors, even if the
rejection handler returned a promise (which presumably should be
adopted).

These were both intertwined to make error and thrown callbacks chain
incorrectly.