mw.loader: Always log exceptions caught from userland callbacks

mw.loader: Always log exceptions caught from userland callbacks

We usually don't catch these at all (not supposed to, as they're
foreign). But in case of handlePending() we catch them because
we need to ensure the state is kept track of properly (an error
is never final in javascript since execution always continues).

However we should at least log it in that case. We already did this
in case of the error() callback, it now does this for the ready()
callback as well.

Bug: 55989
Change-Id: I61f109178833fed60fbba7725fd47b4ff3d2edf4