Exception when updating inner child element attributes from an object property in a repeat

[proppy]

See:
http://codepen.io/anon/pen/syrgJ

It triggers the following exception:

Exception caught during observer callback: Error: Can only reset while open
    at Error (native)
    at Object.T.startReset (http://www.polymer-project.org/platform.js:32:12891)
    at Object.d [as getValueFn_] (http://www.polymer-project.org/platform.js:37:26141)
    at Object.B.discardChanges (http://www.polymer-project.org/platform.js:32:13941)
    at b (http://www.polymer-project.org/components/polymer/polymer.js:32:4884)
    at inner-test.d.bindProperty (http://www.polymer-project.org/components/polymer/polymer.js:32:6211)
    at inner-test.h.bind (http://www.polymer-project.org/components/polymer/polymer.js:32:7561)
    at inner-test.a.(anonymous function) [as bind] (http://www.polymer-project.org/components/polymer/polymer.js:32:19914)
    at w (http://www.polymer-project.org/platform.js:37:1877)
    at A (http://www.polymer-project.org/platform.js:37:2790) 

It seems that startReset is called on a CompoundObserver on which open has never been called.

[sorvell]

The test is working now. Please re-open if the problem resurfaces.