Steps to reproduce :

- import the Mecanim project from the Asset Store
- create a new Animation Controller
- create a new Blend Tree and assign 3 motions to it
- create 2 float parameters and change to 2D Simple Directional
- switch between the parameters and notice the warnings in the console

Other errors occur once the parameter warnings are triggered :

- moving the red dot in the Inspector will spam the console with warnings
- on OSX there is an extra error (screenshot attached)
- pressing Shift + Space to maximize windows now produce window errors in the console

Note :
Regression from 4.6b5.