changing the name of an assigned parameter, then generates an error at runtime...

"BlendTree "Blend Tree" in state "viz" in Controller "" uses parameter "test" which does not exist."

... in this case, the "Blend Tree" state in Controller "testcontroller" uses parameter "test" which DOES exist.
- what is "viz"?
- what is Controller ""

repro:
-create an Animator Controller
-in the controller, RMB > Create State > From New Blend Tree
(this also creates a "Blend" parameter on the controller, expected)
-double-click the Blend Tree state and select the Blend Tree node inside it.
-click Editor Play and notice that there is no error in the console. Stop runtime.
-click the Parameters tab of the controller and rename the "Blend" param to "test".
-click Editor Play... error
bug: "BlendTree "Blend Tree" in state "viz" in Controller "" uses parameter "test" which does not exist."
see attached gif
expected result: no error message since the param does exist.

found in...
Version 5.6.0f1 (95292252f04a)
Branch: 5.6/staging

not repro in Version 5.5.2p2 (03f34082a9c0)