[geary/wip/765516-gtk-widget-conversation-viewer: 151/169] Fix a possible critical error.

[Michael Gratton <mjog src gnome org>]

commit 41e73f17cd5514b1086beda8096176930f9cb597
Author: Michael James Gratton <mike vee net>
Date:   Wed Sep 7 10:37:18 2016 +1000

    Fix a possible critical error.

 src/engine/app/app-conversation.vala |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)
---
diff --git a/src/engine/app/app-conversation.vala b/src/engine/app/app-conversation.vala
index bb96a54..cb9b2c8 100644
--- a/src/engine/app/app-conversation.vala
+++ b/src/engine/app/app-conversation.vala
@@ -186,13 +186,15 @@ public class Geary.App.Conversation : BaseObject {
         
         return email;
     }
-    
+
     public bool is_in_current_folder(Geary.EmailIdentifier id) {
         Gee.Collection<Geary.FolderPath>? paths = path_map.get(id);
-        
-        return (paths != null && paths.contains(owner.folder.path));
+
+        return (paths != null &&
+                owner != null &&
+                paths.contains(owner.folder.path));
     }
-    
+
     /**
      * Return all Message IDs associated with the conversation.
      */