non-fetchable database references displayed in the 'get crossreferences submenu'

This seems to be a regression bug from 2.7 (due to JAL-972, possibly).
Symptoms: 'Get Cross-References' entry shown in the Calculations menu of the alignment window, and includes cross-references for non-fetchable databases.

Steps to reproduce:
0. add internal das sequence and features source: atbdb to jalview's das registry.
1. import sequence 'atb499' from internal Tbrucei DAS source.
2. Open calculation menu - GeneDB link will be shown.

Other info: saving and loading project results in the cross-reference menu entry disappearing, but the sequence has a 'GENEDB' rather than a 'GeneDB' cross reference.