How to add a value in an empty field in MySQL?

I'm running a query that needs to get the first 5 lines with limit 5 . However, there are times when they will return less than 5 lines. The value is empty, neither NULL , nor 0 .

I try to make a case when , but it keeps returning empty. Does anyone know how I can resolve this?

My query is below:

select case when defail5  then 0 else defail5 end 
  from (select failure, count(failure) as defail5 
          from reparo.falhas_consolidadas 
         where  brand2 in ('LBG_DKT') 
           and week = 'week-5-16' 
         group by failure 
         order by count(failure) desc limit 4 offset 3) as tb1;