Cannot select "unknown" person

Double-clicking on an "unknown" doesn't switch, even if kids are involved.

See index7_kbr.ged, Gerald Eugene Lucas [I5]. Should be able to double-click on his "unknown" spouse to see only that sub-tree.

Start by opening index7_kbr.ged and reproducing the double-click behavior for Gerald Eugene Lucas [I5]'s "unknown" spouse, including the case where children are involved. Compare it with double-clicking a known person and verify that the selected view contains only that spouse's subtree when done.

Written by the indexing model from the issue text.