Fix nil delete

src/modules/cron.nim

@@ -33,8 +33,9 @@ proc workerProc() {.thread.} =
                     await stompClient.message("/queue/" & cron.reminder.username, $$c.reminder.toNotificationDTO)
                 logger.log lvlInfo, &"Reminder {cron.id} sent to {cron.reminder.username} for time {targetTime} at ", now()
                 dispatchedReminders.excl cron.id
+                var reminder = cron.reminder
                 dbConn.delete(cron)
-                dbConn.delete(cron.reminder)
+                dbConn.delete(reminder)
                 break
             
             await sleepAsync nextBeat.inMilliseconds.int