Demo: http://jsfiddle.net/e9e2bw6v/2/

We have list, which is under watching. In watch we just replace text:null to text: 'some text'.

When we add an item, and later we clear list, we see error.

We have html:
<div v-if="list.length">
<div v-if="list[0].text">
{{list[0].text}}
</div>
</div>

If we remove second condition, we will not have error.

If you replace 2 conditions to 1 <div v-if="list.length && list[0].text">, we will not have error.

I cannot explain this, but its wrong.

P.S. Sory for bad english.