Fixes scope issue causing login prelim return on Blue

missing scope on a hide() caused a situation where if you viewed a file from a ShareRoom then went back to the login screen, the "X" button sending you to the prelim screen reappeared.
Merge pull request #524 from SpiderOak/css-selector-scope-issue-causes-login-cancel-to-reappear

Fixes scope issue causing login prelim return on Blue