[geary/wip/730682-refine-convo-list] Fix "no conversation selected" exiting selection mode w/ autoselect.

[Michael Gratton <mjog src gnome org>]

commit bdac5e4020f43f5e40af965ca68705a16249f7e7
Author: Michael James Gratton <mike vee net>
Date:   Wed Jan 3 22:41:26 2018 +1100

    Fix "no conversation selected" exiting selection mode w/ autoselect.

 src/client/components/main-window.vala |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)
---
diff --git a/src/client/components/main-window.vala b/src/client/components/main-window.vala
index 9466629..f295e0a 100644
--- a/src/client/components/main-window.vala
+++ b/src/client/components/main-window.vala
@@ -854,7 +854,6 @@ public class MainWindow : Gtk.ApplicationWindow {
         get_action(ACTION_SELECTION_MODE_ENABLE).set_enabled(!enabled);
         this.main_toolbar.set_selection_mode_enabled(enabled);
         this.conversation_list.set_selection_mode_enabled(enabled);
-        this.conversation_viewer.show_none_selected();
         query_supported_actions();
     }
 
@@ -964,11 +963,11 @@ public class MainWindow : Gtk.ApplicationWindow {
 
     private void on_conversation_items_marked(Gee.List<ConversationListItem> marked,
                                               Gee.List<ConversationListItem> unmarked) {
+        Geary.App.Conversation? last_marked = null;
         if (!marked.is_empty) {
-            show_conversation(marked.last().conversation);
-        } else {
-            this.conversation_viewer.show_none_selected();
+            last_marked = marked.last().conversation;
         }
+        show_conversation(last_marked);
         this.main_toolbar.update_selection_count(
             this.conversation_list.get_marked_items().size
         );