shallowMount does not correctly pass refs for functional components

[xanf]

Version

1.0.0-beta.29

Reproduction link

https://codesandbox.io/s/shallowmount-functional-refs-test-38fre

(see tests tab)

Steps to reproduce

1. Create functional component which passes ref to its direct child
2. Try to shallowMount component, with ref to functional component, created on step 1

What is expected?

ref to functional component is valid

What is actually happening?

ref is undefined