NSS: Fix warning access array with index then check
    
    Reported by:cppcheck
    
    Defensive programming: The variable 'i' is used as an array index
    before it is checked that is within limits. This can mean that the array might
    be accessed out of bounds.
    
    This patch eorder condition such as '(a[i] && i 
    (i < blen && a[i]). That way the array will not be accessed if the index
    is out of limits.
    
    Reviewed-by: Michal Žídek <mzidek@redhat.com>