port changes from wlmcewen/octopus v0.6.x

Author: bhornseth

lib/octopus/abstract_adapter.rb

@@ -25,6 +25,7 @@ def self.included(base)
       end
 
       def octopus_shard
+        return {} if @config.nil?
         @config[:octopus_shard]
       end