Quick fix for the reporters issue #263

This really is more of a workaround rather then proper fix. Dredd needs
to refactor and rework of the language hooks handling, especially
graceful stopping as `SIGKILL` is definitely not the way to go.

src/hooks-worker-client.coffee

@@ -61,7 +61,7 @@ handler.stderr.on 'data', (data) ->
 
 handler.on 'close', (status) ->
   console.log "Hook handler exited with status: #{status}"
-  if status != 0
+  if status != 0 || status != null
     hooks.processExit 2
 
 handler.on 'error', (error) ->