Fix Oban warnings

lib/pleroma/workers/cron/clear_oauth_token_worker.ex

@@ -16,6 +16,8 @@ defmodule Pleroma.Workers.Cron.ClearOauthTokenWorker do
   def perform(_opts, _job) do
     if Config.get([:oauth2, :clean_expired_tokens], false) do
       Token.delete_expired_tokens()
+    else
+      :ok
     end
   end
 end

lib/pleroma/workers/cron/digest_emails_worker.ex

@@ -37,6 +37,8 @@ def perform(_opts, _job) do
       )
       |> Repo.all()
       |> send_emails
+    else
+      :ok
     end
   end
 

lib/pleroma/workers/cron/new_users_digest_worker.ex

@@ -55,7 +55,11 @@ def perform(_args, _job) do
         |> Repo.all()
         |> Enum.map(&Pleroma.Emails.NewUsersDigestEmail.new_users(&1, users_and_statuses))
         |> Enum.each(&Pleroma.Emails.Mailer.deliver/1)
-      end
+      else
+        :ok
+      end
+    else
+      :ok
     end
   end
 end

lib/pleroma/workers/cron/purge_expired_activities_worker.ex

@@ -23,6 +23,8 @@ defmodule Pleroma.Workers.Cron.PurgeExpiredActivitiesWorker do
   def perform(_opts, _job) do
     if Config.get([ActivityExpiration, :enabled]) do
       Enum.each(ActivityExpiration.due_expirations(@interval), &delete_activity/1)
+    else
+      :ok
     end
   end