nested track-by breaks when replacing the whole object

[nkovacs]

I don't know if I'm doing something wrong, but this breaks if you click the button a couple times:
http://jsfiddle.net/nkovacs/c08kdyka/

The most common error is "Uncaught TypeError: Cannot read property '__vue__' of null"., but there are others too.

If I remove the v-repeat of subitems, or remove the outer track-by directive, it works.

[nkovacs]

More reproducible errors without the random:
The first item has 0 subitems, then gets 2 the second time you click the button: http://jsfiddle.net/nkovacs/c08kdyka/2/
The first item has 1 subitem, then gets 2 the second time you click the button:
http://jsfiddle.net/nkovacs/c08kdyka/3/

[nkovacs]

Ok, I figured it out: here vm._reused is true, but it should be false. The reason: it inherits _reused from the parent vm, which has it because it's also using track-by.

[yyx990803]

Thanks for digging in and fixing this!