[geary/geary-0.12] Fix another avatar-related critical.

[Michael Gratton <mjog src gnome org>]

commit 0a036e0813aa3f594e2237e45e473ed87d66658a
Author: Michael James Gratton <mike vee net>
Date:   Fri Dec 8 00:00:48 2017 +1100

    Fix another avatar-related critical.
    
    * src/client/conversation-viewer/conversation-message.vala
      (ConversationMessage.load_avatar): We are very occasionally getting
      crashes calling Gtk.Image.get_pixel_size() due to the image is null -
      maybe a race? This obviates the problem by hard-coding the size instead
      of dynamically getting it.

 .../conversation-viewer/conversation-message.vala  |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)
---
diff --git a/src/client/conversation-viewer/conversation-message.vala 
b/src/client/conversation-viewer/conversation-message.vala
index 55f77c9..922b172 100644
--- a/src/client/conversation-viewer/conversation-message.vala
+++ b/src/client/conversation-viewer/conversation-message.vala
@@ -435,10 +435,18 @@ public class ConversationMessage : Gtk.Grid {
      */
     public async void load_avatar(ConversationListBox.AvatarStore loader,
                                   Cancellable load_cancelled) {
+        const int PIXEL_SIZE = 32;
         Geary.RFC822.MailboxAddress? primary = message.get_primary_originator();
         if (primary != null) {
             int window_scale = get_scale_factor();
-            int pixel_size = this.avatar.get_pixel_size() * window_scale;
+            // We occasionally get crashes calling as below
+            // Gtk.Image.get_pixel_size() when the image is
+            // null. There's perhaps some race going on there. So we
+            // need to hard-code the size and keep it in sync with
+            // ui/conversation-message.ui. :(
+            //
+            //int pixel_size = this.avatar.get_pixel_size() * window_scale;
+            int pixel_size = PIXEL_SIZE * window_scale;
             try {
                 Gdk.Pixbuf? avatar_buf = yield loader.load(
                     primary, pixel_size, load_cancelled