Use `id` from `source_user` inside query

With the proper presence check using `source_user_id` we guarantee `source_user` is there, and so we can use it like in the other query

lib/use_case/question/create.rb

@@ -83,7 +83,7 @@ module UseCase
       def filtered?(question)
         target_user.mute_rules.any? { |rule| rule.applies_to? question } ||
           (anonymous && AnonymousBlock.where(identifier: question.author_identifier, user_id: [target_user.id, nil]).any?) ||
-          (source_user_id && anonymous && AnonymousBlock.where(target_user_id: [source_user_id, nil], user_id: [target_user.id, nil]).any?)
+          (source_user_id && anonymous && AnonymousBlock.where(target_user_id: [source_user.id, nil], user_id: [target_user.id, nil]).any?)
       end
 
       def source_user