Save line

[jburel]

Problem found while debugging the delete ROI error:

To test the PR:

• Draw a line and Save
• Turn the line into a Polyline and Save. No error message displayed.
• Propagate the shape and Save
• Go to one plane, remove the shape. Go to another plane and delete the shape. Save
• Check that the roi is correctly saved.

[gusferguson]

@jburel
Tested using OMERO.insight-5.0.2-132-41d6e23-ice35-b27-mac octopus user-3 read-annotate-1

Draw a line and Save
Turn the line into a Polyline and Save
- no error message displayed.
Propagate the shape and Save
Go to one plane, remove the shape. Go to another plane and delete the shape. Save
- deleted in ROI manager pane - right click and using keyboard delete
- deleted via right click in viewer window
- deleted via ROI assistant
Check that the roi is correctly saved.

No error messages and all saved fine.

Behaves as expected.
Good to merge

[jburel]

--rebased-to #2626