Steps to reproduce:

1. Open Unity;
2. Create new project;
3. Import attached 'animatorTest.unitypackage' package;
4. In the Project go to Assets -> Slenderman;
5. Open SlenderController.controller;
6. In the animator window double click on any grey state (Pose, Walk etc);
7. Observe console.

Actual result:

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

is shown when selecting animator state. See attached video and actual.png screenshot.

Regression introduced in Unity 5.4.0.

Expected result:
Errors should not be shown after picking animator state.

Notes:
- Reproducible in: 5.4.0b6, 5.4.0b5;
- Reproducible in OSX 10.11.3 and Windows 10;
- Not reproducible in: 5.3.2f1, 5.3.1f1;
- Error is shown when double clicking on animator state only for the first time, further clicking doesn't throw that error;
- Error is also shown when entering play mode after picking animator state.