RecastNavMesh fails to delete when grouped with NavMeshBoundsVolume - Top Down project

While testing in //UE4/Release-4.16 CL 3466753 in Binary – I encountered an issue when deleting NavMeshBoundsVolume and RecastNavMesh. The NavMeshBoundsVolume is deleted but the RecastNavMesh remains.

Regression: No
This issue also occurs in //UE4/Main and //UE4/Release-4.15

1. Open UE4 Editor
2. Create a new Blueprint Top Down project
3. In the World Outliner, type "Nav"
4. Select both 'NavigationMeNavMeshBoundsVolume' & 'RecastNavMesh-Default'
5. Press the Delete key

Result:
MeshBoundsVolume is deleted, but RecastNaveMesh remains.
Expected Result:
MeshBoundsVolume and RecastNaveMesh are deleted without error or warnings.
Frequency:
4/4