Steps to reproduce:

1. Open Unity;
2. Open attached project and 'test.unity' scene;
3. Drag any SpeedTree .spm model (for instance, 'Broadleaf_Mobile.spm') from 'Free_SpeedTrees' folder to the Scene view;
4. Enter Play mode;
5. In the Scene view click twice on the SpeedTree model to select its LOD0 level in the Scene view;
6. Observe the console and SceneView rendering.

Actual result:
Weird uninformative error:

GetLocalizedString is not allowed to be called from a MonoBehaviour constructor, call it in Awake or Start instead. Called from script 'TreeEditor' on game object ''.
See "Script Serialization" page in the Unity Manual for further details.
UnityEditor.LocalizationDatabase:GetLocalizedString(String)
TreeEditor.TreeEditor:.cctor()

is shown in the console.

Also in some cases tree shadows rendering gets corrupted - it starts to blink (doesn't reproduce always).
See attached gif video for clarity.

Regression introduced in 5.4.0b1.

Expected result:
Uninformative error should not be displayed when picking SpeedTree LOD level in Play mode.

Notes:
- Doesn't reproduce in 5.4.0a6 and 5.3.0f4;
- Reproduces on both Windows 10 and OSX 10.10.2;
- Also reproduces when selecting any SpeedTree's LOD level in the Hierarchy view and entering Play mode;
- Also reproduces for tree models created within Unity's Tree Creator when entering play mode and picking them in Scene View;
- Also similar error is thrown when dragging Sprites to the scene view.