[DAR-1165][DAR-1734][External] Polygons from other plane export correctly

[shernshiou]

Problem

The polygons at Coronal and Sagittal are not exported.

Solution

Go through all the slots to ensure all the polygons are exported.

Fixes DAR-1165 Fixes DAR-1734

Changelog

• Polygon from Coronal and Sagittal plane are exported correctly.

[linear[bot]]

DAR-1165 BUG: Only Axial annotations are exported fron NPR views with polygon annotations

[shernshiou]

Result

[linear[bot]]

DAR-1734 BUG: Nifti exports are either empty or have annotations at one slice per volume