`_scopeId` lost for child components with falsy v-if on root elements

[kazupon]

Vue.js version

2.2.10

Reproduction Link

http://jsfiddle.net/su5aLp3a/21/

Steps to reproduce

1. uncheck show child checkbox
2. check show child checkbox

What is Expected?

expect parent _scopeId and child _scopeId into root element on child component (in repro code, data-v-00001 and data-v-00002)

What is actually happening?

lost parent _scopeId from root element on child component (in repro code, data-v-00002 only)

Related issue

See vuejs/vue-loader#576