(maint) Catch everything in query middleware
(maint) Catch everything in query middleware

In order to safely `assert` things in the query code, we need to ensure
that we do not leak AssertionErrors, which are not caught by `catch
Exception`. Add catch Throwable as a catch-all backstop to
any other thing that could be thrown.

puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb