Crash report: http://pastebin.com/N51U6v7v
I created a new project using BP FPS template and I needed to remove all assets from it (to have a totally blank project where I can migrate my 4.12 project). After selecting all assets in the Content browser and pressing delete key, i was asked to force delete assets, which I said yes to and engine crashed.
I did the same kind of thing in Pre1 and in any previous builds of UE4 and I never had a crash.
I also tried deleting actors from the level before deleting assets from the content browser and I still get crash when assets get deleted.