Fix sidebar (and content) height
Fix sidebar (and content) height

Summary: When expanding the sidebar, sometimes the sign in / profile button would disappear, as the main content would be to height

Reviewed By: passy

Differential Revision: D20534482

fbshipit-source-id: 6248df501afcefc4afb6df3a6fd864462f8290e4

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper