Fixed an issue caused by smembers returning nil rather than an empty Array in some older versions of Redis.

lib/redistat/key.rb

@@ -53,7 +53,8 @@ module Redistat
     end
     
     def children
-      db.smembers("#{scope}#{LABEL_INDEX}#{@label}").map { |member|
+      members = db.smembers("#{scope}#{LABEL_INDEX}#{@label}") || [] # older versions of Redis returns nil
+      members.map { |member|
         child_label = [@label, member].reject { |i| i.nil? }
         self.class.new(self.scope, child_label.join(GROUP_SEPARATOR), self.date, @options)
       }