Null values for `v-text` directive not handled in SSR

[pi0]

Version

2.4.2

Reproduction link

https://glitch.com/edit/#!/v-text

https://v-text.glitch.me/html
https://v-text.glitch.me/text

Steps to reproduce

Try to render <span v-text="x"></span> where x is is null or undefined

What is expected?

It may be gracefully handled just like v-html directive (see notes below) or client side version of v-text.

What is actually happening?

Throwing an internal TypeError:

Cannot read property 'replace' of undefined

function escape (s) {
  return s.replace(/[<>"&]/g, escapeChar)
}

---

Seems the simple fix would be defining a default value for s parameter in util.js (or better do a string type check on value)

Related to nuxt/nuxt#1638

Some Notes

v-html behaviour also differs in SSR and client. SSR renders v-html: <span>null</span> while it changes into <span></span> on client side. Seems <span v-html="foo"> is being optimized into '<span>' + (_vm.foo). So we can change it into (_vm.foo|| '') to handle this inconsistency during SSR render.