Steps to reproduce:

1. Open Unity;
2. Open attached 'massplacetreesbug.unity' package;
3. Open 'test.unity' scene;
4. Select Terrain gameobject in the Hierarchy view;
5. Go to "Paint Trees' tab of the terrain's Inspector component;
6. Select 'Broadleaf_Desktop' tree model;
7. Click 'Mass Place Trees';
8. Input any number bigger than 100 (around 150 would give a repro);
9. Click 'Place' button;
10. Scroll out in the Scene view.

Actual result:
Unity crashes. See attached gif video.

In the stacktrace following could be observed:

0x00000001400D27A3 (Unity) ShaderLab::TexEnv::SetTextureInfo
0x000000014011719F (Unity) std::_Pop_heap_0<RenderPassData * __ptr64,RenderPassData,ForwardShaderRenderLoop::RenderObjectSorter<0> >
0x000000014032068C (Unity) GfxDevice::ExecuteAsync
0x000000014011783B (Unity) ForwardShaderRenderLoop::PerformRendering

Regression introduced in Unity 5.4.0a5, probably affected by race conditions in multithreaded code.

Notes:
- Happens only on Windows (10 and 8.1 checked). Doesn't seem to happen on OSX;
- Reproduces in 5.4.0b7, 5.4.0b5, 5.4.0b4, 5.4.0a5;
- Doesn't reproduce in 5.4.0a4;
- Happens only with realtime lighting. Doesn't seem to happen when lighting mode is set to Baked.