Union problem in mysql

I am trying to perform a query and is giving the following error:

  

Unknown column 'FILIAL' in 'field list'

The query is as follows:

SELECT TICKET, DATAHORA, TIPO, ESTADO, CRITICIDADE, LOGIN, PARECER, INFOPEND, PROP, DATAPROP, PREV, SRD, PROT, REAB,FILIAL
FROM (
SELECT 
      TC.TN TICKET, TC.CREATE_TIME DATAHORA,  TT.NAME TIPO, TS.NAME ESTADO, TP.NAME CRITICIDADE, US.LOGIN LOGIN,
      CASE  
        WHEN TH.NAME LIKE  '%PARECER%' THEN RIGHT(TH.NAME, POSITION('%' IN REVERSE(TH.NAME))-1)
        ELSE ''
        END PARECER,
      CASE  
        WHEN TH.NAME LIKE  '%INFORMACOESPENDENTES%' THEN RIGHT(TH.NAME, POSITION('%' IN REVERSE(TH.NAME))-1)
        ELSE ''
        END INFOPEND,
      CASE  
        WHEN AR.A_SUBJECT LIKE  '%ATUALIZAÇÃO PROPRIETÁRIO%' THEN LEFT(AR.A_FROM, POSITION('<' IN (AR.A_FROM))-1)
        ELSE ''
        END PROP,
      CASE  
        WHEN AR.A_SUBJECT LIKE  '%ATUALIZAÇÃO PROPRIETÁRIO%' THEN (AR.CREATE_TIME)
        ELSE ''
        END DATAPROP,
      CASE  
        WHEN TH.NAME LIKE  '%PREVISAOATENDIMENTO%' THEN RIGHT(TH.NAME, POSITION('%' IN REVERSE(TH.NAME))-1)
        ELSE ''
        END PREV,
      CASE  
        WHEN TH.NAME LIKE  '%SRD%' THEN RIGHT(TH.NAME, POSITION('%' IN REVERSE(TH.NAME))-1)
        ELSE ''
        END SRD,
      CASE  
        WHEN TH.NAME LIKE  '%PROTOCOLO%' THEN RIGHT(TH.NAME, POSITION('%' IN REVERSE(TH.NAME))-1)
        ELSE ''
        END PROT,
      CASE  
        WHEN TS.NAME LIKE  '%REABERTO' THEN (TS.NAME)
        ELSE ''
        END REAB

   FROM OTRS2.TICKET TC
   INNER JOIN OTRS2.TICKET_TYPE TT ON TC.TYPE_ID = TT.ID
   INNER JOIN OTRS2.TICKET_STATE TS ON TC.TICKET_STATE_ID = TS.ID
   INNER JOIN OTRS2.TICKET_PRIORITY TP ON TC.TICKET_PRIORITY_ID=TP.ID
   INNER JOIN OTRS2.USERS US ON TC.CREATE_BY=US.ID
   INNER JOIN OTRS2.TICKET_HISTORY TH ON TC.ID=TH.TICKET_ID 
   INNER JOIN OTRS2.ARTICLE AR ON TC.ID=AR.TICKET_ID
   UNION 
        SELECT NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, CUSTOMER.LOGIN FILIAL FROM OTRS2.CUSTOMER_USER CUSTOMER
 ) A

PS: Until I put UNION , the query was working fine and returning the results.