How to reproduce the problem

1) Create new java desktop application.
2) For application shell chose Database application
3) In Master Table Step: try to select new database connection in database connection combo box
4) In new database connection form select java db embedded
5) In database name type something that is not exist  
6) enter a password and click OK
7) you can see the error message that say database is not exist, fine!
8) click OK, and then cancel the new database connection dialog
9) try from step 3 again and again
for every try you have redundant connection entry in new database connection - name combo box

see the attachment