Steps to repro:

1. Open Unity;
2. Open attached project and 'test.unity' scene;
3. Select 'Tree1' gameobject in the Hierarchy view;
4. Either toggle any setting in the tree creator (for example, Distribution section) or click on tree root node on the graph;
5. Observe tree rendering.

Actual result:
Tree and leaf rendering breaks. Only tree mesh is visible, without textures and UV's. See attached gif video and actual_treecreator screenshot.

Expected result:
Tree and leaf rendering should not break after toggling tree settings in Inspector (see attached expected_treecreator screenshot).

Notes:
- Reproduces on both OSX 10.11.3 and Windows 10;
- Reproduces on 5.4.0b5, 5.4.0b4, 5.3.2f1; On 5.3.1f1 tree leaves are not rendered after dragging them to the scene;
- Undoing setting toggling doesn't restore prefab rendering.