Fix errors when multiple Delete are received for a given actor (#17460)

app/workers/activitypub/processing_worker.rb

@@ -6,7 +6,10 @@ class ActivityPub::ProcessingWorker
   sidekiq_options backtrace: true, retry: 8
 
   def perform(account_id, body, delivered_to_account_id = nil)
-    ActivityPub::ProcessCollectionService.new.call(body, Account.find(account_id), override_timestamps: true, delivered_to_account_id: delivered_to_account_id, delivery: true)
+    account = Account.find_by(id: account_id)
+    return if account.nil?
+
+    ActivityPub::ProcessCollectionService.new.call(body, account, override_timestamps: true, delivered_to_account_id: delivered_to_account_id, delivery: true)
   rescue ActiveRecord::RecordInvalid => e
     Rails.logger.debug "Error processing incoming ActivityPub object: #{e}"
   end