[Fiber] fix ensure class components refs get re-assigned to emptyObject on mount#9045

trueadm merged 6 commits intofacebook:masterfacebook/react:masterfrom

trueadm:emptyObject-reference-mismatch-due-to-mockingtrueadm/react:emptyObject-reference-mismatch-due-to-mockingCopy head branch name to clipboard