Allow modeling pets for colors we haven't gotten metadata for yet

This used to be the behavior, and the site has plenty of graceful
fallbacks for it, I just forgot this one when doing Rails upgrades!

Note that the impress-2020 stuff is *not* as graceful about this, so
the wardrobe page won't show the pet until the color is in the DB. Ah
well, still an improvement!

app/models/pet.rb

@@ -86,8 +86,8 @@ class Pet < ApplicationRecord
   def wardrobe_query
     {
       name: self.name,
-      color: self.pet_type.color.id,
-      species: self.pet_type.species.id,
+      color: self.pet_type.color_id,
+      species: self.pet_type.species_id,
       pose: self.pet_state.pose,
       state: self.pet_state.id,
       objects: self.items.map(&:id),

app/models/pet_type.rb

@@ -3,8 +3,12 @@ class PetType < ApplicationRecord
   IMAGE_CP_LOCATION_REGEX = %r{^/cp/(.+?)/[0-9]+/[0-9]+\.png$};
   IMAGE_CPN_ACCEPTABLE_NAME = /^[a-z0-9_]+$/
 
-  belongs_to :species
-  belongs_to :color
+  # NOTE: While a pet type does always functionally belong to a color and
+  # species, sometimes we don't have that record yet, in which case color_id
+  # or species_id will refer to a nonexistant record, and the site should
+  # generally fall back gracefully about that.
+  belongs_to :species, optional: true
+  belongs_to :color, optional: true
   has_one :contribution, :as => :contributed, :inverse_of => :contributed
   has_many :pet_states
   has_many :pets