Some of the unit tests will undef the adaptor.  Make the canonical_transcript() method warn about not being able to fetch the canonical transcript when there's no adptor attached to the gene.
Some of the unit tests will undef the adaptor.  Make the
canonical_transcript() method warn about not being able to fetch the
canonical transcript when there's no adptor attached to the gene.

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