Added tests for null values before writing to the db.
Added tests for null values before writing to the db.

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