- formatter => sub { my ($input) = @_; return trim(DateTime->from_kivitendo($input)->strftime('%e%m%y')) },
- valid_check => sub { my ($check) = @_; return ($check =~ m/^[0-9]{5,6}$/) },
+ formatter => sub { my ($input) = @_; return undef unless $input; return trim(DateTime->from_kivitendo($input)->strftime('%e%m%y')) },
+ valid_check => sub { my ($check) = @_; return 1 unless $check; return ($check =~ m/^[0-9]{5,6}$/) },