Fallback to old on-the-fly URI for follows/blocks if no stored URI (#7371)

Fix #7367

app/serializers/activitypub/block_serializer.rb

@@ -5,7 +5,7 @@ class ActivityPub::BlockSerializer < ActiveModel::Serializer
   attribute :virtual_object, key: :object
 
   def id
-    [ActivityPub::TagManager.instance.uri_for(object.account), '#blocks/', object.id].join
+    ActivityPub::TagManager.instance.uri_for(object) || [ActivityPub::TagManager.instance.uri_for(object.account), '#blocks/', object.id].join
   end
 
   def type

app/serializers/activitypub/follow_serializer.rb

@@ -5,7 +5,7 @@ class ActivityPub::FollowSerializer < ActiveModel::Serializer
   attribute :virtual_object, key: :object
 
   def id
-    ActivityPub::TagManager.instance.uri_for(object)
+    ActivityPub::TagManager.instance.uri_for(object) || [ActivityPub::TagManager.instance.uri_for(object.account), '#follows/', object.id].join
   end
 
   def type