fix for VariationFeatures using a fake adaptor on circular slices
fix for VariationFeatures using a fake adaptor on circular slices

muffato/ensembl,muffato/ensembl,muffato/ensembl,Ensembl/ensembl,james-monkeyshines/ensembl,james-monkeyshines/ensembl,danstaines/ensembl,Ensembl/ensembl,muffato/ensembl,danstaines/ensembl,Ensembl/ensembl,james-monkeyshines/ensembl,james-monkeyshines/ensembl,danstaines/ensembl,Ensembl/ensembl