dmails: fixup exceptions when verifying dmail keys.

Fix show action throwing exceptions when viewing a dmail without a dmail key.

app/logical/danbooru/message_verifier.rb

@@ -15,5 +15,9 @@ module Danbooru
     def verify(*args, **options)
       verifier.verify(*args, purpose: purpose, **options)
     end
+
+    def verified(*args, **options)
+      verifier.verified(*args, purpose: purpose, **options)
+    end
   end
 end

app/models/dmail.rb

@@ -121,7 +121,7 @@ class Dmail < ApplicationRecord
     end
 
     def valid_key?(key)
-      id == verifier.verify(key)
+      id == verifier.verified(key)
     end
 
     def visible_to?(user, key)