[css] Fix for z-index issue making compose un-clickable
[css] Fix for z-index issue making compose un-clickable

nylas/inbox-scaffold-html5,PriviPK/privipk-webapp,Eagles2F/inbox-scaffold-html5,PriviPK/privipk-webapp,Eagles2F/inbox-scaffold-html5,nylas/inbox-scaffold-html5,PriviPK/privipk-webapp,nylas/inbox-scaffold-html5,Eagles2F/inbox-scaffold-html5,PriviPK/privipk-webapp