Steps to reproduce:

1. Open Unity;
2. Open attached project and 'Untitled.unity' scene;
3. Open Lighting tab in the Inspector;
4. Press Build button to start building baked lightmap;
5. Press Cancel button at 'Visibility' calculation stage to stop baking lightmap;
6. Press arrow button on the right side of Build button to open the dropdown list;
7. Press 'Clear Baked Data';

8. Notice that uninformative m_SystemData.empty()
UnityEditor.GenericMenu:CatchMenu(Object, String[], Int32)
has been thrown in the console (see attached actualVisibilityCalculation.png screenshot).

9. Press Build again;
10. Press Cancel button at 'Light Transport' calculation stage to stop baking lightmap;
11. Repeat steps 6 and 7;

12. Notice that uninformative m_PendingRadiositySystemHashes.empty()
UnityEditor.GenericMenu:CatchMenu(Object, String[], Int32)
has been thrown in the console along with the previous error (see attached actualLighttransportCalculation.png screenshot) .

Also see attached gif video.

Expected result:
Uninformative errors should not be displayed when terminating Lighting process and clearing lightmapping data at each stage of lightmap calculation.

Notes:
- Reproduces in 5.4.0b1, 5.4.0a6, 5.3.1p1, 5.2.2p4.
- Reproduces on both Windows 10 and OSX 10.11.2;
- This issue gets mostly annoying when lightmapping scenes with huge gameobjects (like, for instance, terrain);
- This issue doesn't seem to affect lightmapped scene rendering.