If you pick a segment as the audience for a variant, and delete this segment from the Segments app, the reference to the deleted segment is still present. You’d have to manually remove it or select a different segment in order to remove the variant’s segment reference.

Steps
-Create a segment within the Segments App
-Go the Pages App and select a page from the tree that contains a variant. Or Create a page variant if none are present.
-Go to the JCR and check the Segments workspace to take note of the uuid of the segment you made.
-Click “Choose Audience” and select the Segment you have created
-Go back to the Segments App and delete this Segment
-Go back to the Pages app and you will see that the segment is still chosen as the page’s audience
-Further, if you check the JCR, the mgnl:assignedSegments property is still present and its value is the uuid of the deleted segment.

Expected result
When deleting a segment from the Segments App, all references to the deleted segment are removed.

Actual result
When deleting a segment from the Segments App, all references to the deleted segment are still present.

Additional notes
This was tested on 6.2.3 and 5.7.4.