Allow the slice() method to be used to undef the slice ("$f->slice(undef)").
Allow the slice() method to be used to undef the slice
("$f->slice(undef)").

james-monkeyshines/ensembl,mjg17/ensembl,at7/ensembl,danstaines/ensembl,mjg17/ensembl,mjg17/ensembl,willmclaren/ensembl,at7/ensembl,muffato/ensembl,danstaines/ensembl,Ensembl/ensembl,muffato/ensembl,willmclaren/ensembl,Ensembl/ensembl,Ensembl/ensembl,james-monkeyshines/ensembl,muffato/ensembl,muffato/ensembl,danstaines/ensembl,at7/ensembl,james-monkeyshines/ensembl,mjg17/ensembl,james-monkeyshines/ensembl,Ensembl/ensembl,at7/ensembl