fix done not logging when using with_context in a worker

@mperham fixes https://github.com/mperham/sidekiq/issues/2109
I believe `any?` is a Railsism which Sidekiq can't use but I don't think it's necessary if you have c always be non-nil.

```
irb(main):001:0> [].join(" ")
=> ""
irb(main):002:0> ['foo'].join(" ")
=> "foo"
irb(main):003:0> ['foo', 'bar'].join(" ")
=> "foo bar"
```