Don't highlight collections after going back

src/StartupMenu.vala

@@ -121,6 +121,7 @@ namespace Publicate {
                     collection_row.title = collection.name;
                     collection_row.subtitle = collection.domain;
                     collection_row.activatable = true;
+                    collection_row.selectable = false;
                     collection_row.activated.connect(() => window.load_collection.begin(collection));
                     collection_list.append (collection_row);
                 }