fix null zone ID bug

TNT has started serving half-removed Corridor of Chance effects:
it has the asset ID and URL and all, but the zone ID is blank.
RocketAMF has patched the empty key bug, and now we ignore assets
associated with empty keys.

Gemfile.lock

@@ -68,7 +68,7 @@ GIT
 
 GIT
   remote: git://github.com/rubyamf/rocketamf.git
-  revision: 3f16cf841d9c36045f720b307bbffa61fb63a7ac
+  revision: 796f591d002b5cf47df436dbcbd6f2ab00e869ed
   specs:
     RocketAMF (1.0.0)
 

app/models/pet_state.rb

@@ -138,7 +138,7 @@ class PetState < ActiveRecord::Base
   def self.from_pet_type_and_biology_info(pet_type, info)
     swf_asset_ids = []
     info.each do |zone_id, asset_info|
-      if asset_info
+      if zone_id.present? && asset_info
         swf_asset_ids << asset_info[:part_id].to_i
       end
     end
@@ -166,7 +166,7 @@ class PetState < ActiveRecord::Base
     pet_state.pet_type = pet_type # save the second case from having to look it up by ID
     relationships = []
     info.each do |zone_id, asset_info|
-      if asset_info
+      if zone_id.present? && asset_info
         swf_asset_id = asset_info[:part_id].to_i
         swf_asset = existing_swf_assets_by_id[swf_asset_id]
         unless swf_asset