Don't reset active conference when opening the selection page

This is trying to address some confusing behavior with Kongress. Currently if you have an active conference, and click this it will suddenly (and without warning) boot you into an invalid state where some buttons are broken and do nothing - like the "Check for updates" button.

Instead, let's avoid this whole problem by not resetting the active conference when going to this page. Then you can stay on your active conference by clicking something else in the sidebar, canceling the action. This makes the UX feel a little bit better.

(Also sets a better title when no conference is selected.)