[geary/wip/765516-gtk-widget-conversation-viewer: 176/207] Fix a possible crit error.

[Michael Gratton <mjog src gnome org>]

commit c12204d596e7bea30df24ff8b9a5a2fd29b9a068
Author: Michael James Gratton <mike vee net>
Date:   Sat Sep 10 18:22:09 2016 +1000

    Fix a possible crit error.

 .../conversation-viewer/conversation-email.vala    |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/client/conversation-viewer/conversation-email.vala 
b/src/client/conversation-viewer/conversation-email.vala
index b3e302c..35ccab0 100644
--- a/src/client/conversation-viewer/conversation-email.vala
+++ b/src/client/conversation-viewer/conversation-email.vala
@@ -149,6 +149,10 @@ public class ConversationEmail : Gtk.Box {
         }
 
         internal async void load_icon(Cancellable load_cancelled) {
+            if (load_cancelled.is_cancelled()) {
+                return;
+            }
+
             Gdk.Pixbuf? pixbuf = null;
 
             // XXX We need to hook up to GtkWidget::style-set and