Handle invalid Item state a bit better

Catch missing fields in validation before sending it to the DB, and
skip the Dyeworks stuff if the name is missing.

I ran into this looking into `test/trade_activity_test.rb`, which fails
right now because we try to create a boring placeholder item with
minimal fields, which Dyeworks can't call `name.match()` on!

Now, the test fails with a more helpful error about the item being
invalid. Next, I'll fix that!

app/models/item.rb

@@ -23,6 +23,8 @@ class Item < ApplicationRecord
   has_many :dyeworks_variants, class_name: "Item",
     inverse_of: :dyeworks_base_item
 
+  validates_presence_of :name, :description, :thumbnail_url, :rarity, :price,
+    :zones_restrict
 
   attr_writer :current_body_id, :owned, :wanted
 

app/models/item/dyeworks.rb

@@ -117,7 +117,7 @@ class Item
 			)\z
 		}x
 		def inferred_dyeworks_base_item
-			name_match = name.match(DYEWORKS_NAME_PATTERN)
+			name_match = (name || "").match(DYEWORKS_NAME_PATTERN)
 			return nil if name_match.nil?
 
 			Item.find_by_name(name_match["base"])