[AB] AssetBundle crashes ParticleSystem's mesh renderer

Hi,

I'm trying to use AssetBundle to load a prefab, which contains ParticleSystem uses mesh as renderer, and that crashes in every places(Editor, iOS...). I've made a simplified project to reproduce the crash in attachment.

To reproduce:

- Open attached project, open 'Scenes/TestScenes'
- From "AssetBundleUtil" menu item, select 'BuildAB' command based on platform to build AssetBundles. (corresponding code in 'Assets/Scripts/Editor/Builder.cs')
- Run player in editor or build & run
- Click 'Load' button and crash happens.

========
The project contains only one prefab and one FBX file. The
prefab("Resources/TestParticleMeshRenderer.prefab") contains only a
simple ParticleSystem, whose renderer's Render Mode is "Mesh".
It uses the mesh contains in the FBX file("Models/Effect/ring_red03.FBX").

The crash only happens when:
- the mesh is NOT set as 'Read/Write Enabled' in Import Settings
- the prefab contains ParticleSystem and the mesh are built into seperate
AssetBundles

Bug fired:
https://fogbugz.unity3d.com/default.asp?749905_gl56slsmr7s8l10v