Issue Summary

The timeline across the top will no longer be visible (after refreshing the Roadmap) if an Objective Milestone linked to a Capability or any other work item type was displayed in the roadmap and its target Completion Date was later unset.

This is reproducible on Data Center: yes

Steps to Reproduce

1. Create two solution objectives(Cap-Milestone1 and Cap-Milestone2) with the type "Roadmap Milestone" and associate it with two capabilities (Cap1 and Cap2).
2. Set a target completion date for both objectives
3. Set the type to type "Roadmap Milestone" (optional)
   
4. Go to the roadmaps (Work view: Capabilities)
5. Click on the 'Milestones button and toggle 'ON' the "Objective Milestones'
   
6. Click on the 'View' button for both milestones and apply to save the changes
   
7. The milestones appear in the roadmaps
   
8. Go back to one of the objective milestones and remove the 'Target Completion date'
   
9. Go back to the roadmaps and make sure to refresh the page

Expected Results

The roadmap displays the timeline across the top and all milestones with a completion target date

Actual Results

The roadmap does not display the timeline across the top and any milestones.

although only one Milestone is considered incomplete:

The same behavior is seen for other work items (feature or epic).

Workaround

Make sure to not unset the target completion date for the objective milestones that have already been explicitly displayed/shown on the roadmap.