window position not preserved after moving window with gathered views

Noticed whilst testing JAL-1815. Probably a general issue.

1. create a split view alignment, and several views. scatter them liberally around the desktop area.
2. save the project. open in a new instance, gather the views to one window.
3. save the project. open the project in a new instance.
4. expand the views, gather all into *another* view and then save the project.
5. Move the gathered window to another position in the desktop area and save that project.
6. open both projects saved in 4 and 5 in two new jalview instances.
-> The shifted position of the gathered window in 5 is not preserved in the project.