Nil keys break stashes

[kornypoet]

The following creates a difficult situation to recover from if a key is ever nil:

require 'vayacondios-client'
client = Vayacondios::HttpClient.new(host: 'localhost', port: 9000, organization: 'hyrule')
client.set!('topic', 'id', { nil => 'accident' })
client.get('topic', 'id')
#=> {""=>"thing"}
client.set!('topic', 'id.nested', { real: 'value' })
client.get('topic', 'id.nested')
#=> nil

Discovered this by accident, and it prevents further nested use of the topic id pair.

[kornypoet]

This jira claims to have solved the issue for Mongo 2.1.0, but it still persists with our current install of Mongo version 2.2.1.