This is a known problem and I think it has to do with removing the node while its settings are being displayed. The workaround is to delete from the node network view while on a different layout tab than Objects. For example switch to Terrain then find the population in the node network and delete from there. This will leave behind the object that was inside it in the Objects node list and if you click on it it will cause a crash, so it's not a perfect workaround, but it'll do for now.
This problem will definitely be resolved soon.
- Oshyan