Fix attempting to observe non-DOM refs in Link (#7249)
Fix attempting to observe non-DOM refs in Link (#7249)

handleRef isn't called with valid DOM node
azukaru/next.js,flybayer/next.js,flybayer/next.js,azukaru/next.js,azukaru/next.js,BlancheXu/test,JeromeFitz/next.js,flybayer/next.js,JeromeFitz/next.js,zeit/next.js,JeromeFitz/next.js,JeromeFitz/next.js,BlancheXu/test,azukaru/next.js,zeit/next.js,BlancheXu/test,zeit/next.js,flybayer/next.js