In 5.6/trunk, dragging a ScriptableObject asset somewhere in the editor (over hierarchy, or over inspector etc.) crashes the editor. Looks like some new code does not handle the case of ScriptableObjects, which look a lot like MonoBehaviours, not actually being Components that are attached to game objects.

Repro steps:
1. open DragScriptableObject542.zip project (made with 5.4.2 for testing with earlier versions than 5.6)
2. drag MyScriptableObject.asset from project view over other views (e.g. hierarchy or inspector)
3. editor crashes in:

IsUserModifiable (EditorHelper.cpp:198)
MoveComponent (ComponentUtility.cpp:699)
HandleExtractComponentDragAndDrop (DragAndDropForwarding.cpp:1244)
CanHandleExtractComponentDragAndDrop (DragAndDropForwarding.cpp:1266)
DragAndDropForwarding::DispatchDragAndDrop (DragAndDropForwarding.cpp:349)
DragAndDropForwarding::CanHandleDragAndDrop (DragAndDropForwarding.cpp:364)
DragAndDropForwarding::CanHandleDragAndDrop (DragAndDropForwarding.cpp:376)
InternalEditorUtility_CUSTOM_HierarchyWindowDrag(...)

Doing the same in 5.4.2 and 5.5.0 does not crash.
Crashes in 5.6b1-ish build as of 2016 December 6 (6f87e0affcd2)