Relation editor: Connectivity: Problem with dual-carriage, open end on top with only one way for one direction

[skyper]

This is a follow-up of #19633, under special condition.

What steps will reproduce the problem?

1. Have a route=road relation with both ends split per direction and open ended and at least one of the direction branch consisting of only one way. See example file​
2. Sort the relation in relation manager
3. Look at the connectivity displayed on the start/end
4. Sort again (all members are flipped)
5. Look again at the start/end.

What is the expected result?

Complete connection displayed on all ends.

What happens instead?

Only on top and with at least only one direction branch consisting of only one way, connectivity is broken and "jump to gap" interprets it as gap.

Please provide any additional information below. Attach a screenshot if possible.

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-03-14 18:17:35 +0100 (Sun, 14 Mar 2021)
Revision:17560
Build-Date:2021-03-14 17:21:03
URL:https://josm.openstreetmap.de/svn/trunk