Summary: The misbehavior came from undefined height and width inside `Sidebar` component. This is fixed by put it in the container that expands through whole `Sidebar`.
Reviewed By: Andrey-Mishanin
Differential Revision: D23954008
fbshipit-source-id: 9c096a8f3141a012a2a1ab32c2d5e689e7bde396
95ae7a8bce