[evolution/gnome-3-22] Fix a use-after-free after editor's WebKitWebProcess crash ]I[

[Milan Crha <mcrha src gnome org>]

commit 4ac0ca465f73a634737ec51156a854fae454f1de
Author: Milan Crha <mcrha redhat com>
Date:   Mon Dec 19 17:22:12 2016 +0100

    Fix a use-after-free after editor's WebKitWebProcess crash ]I[
    
    Correct a regression, which could mean that the first attempt to open
    a composer window could result in an infinite wait, while the other
    attempts worked just fine. There was also an error printed on
    the evolution exit, about the shell not being finalized.

 modules/webkit-editor/e-webkit-editor.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)
---
diff --git a/modules/webkit-editor/e-webkit-editor.c b/modules/webkit-editor/e-webkit-editor.c
index 69a0d6f..08b4dd5 100644
--- a/modules/webkit-editor/e-webkit-editor.c
+++ b/modules/webkit-editor/e-webkit-editor.c
@@ -615,11 +615,15 @@ web_extension_vanished_cb (GDBusConnection *connection,
 {
        g_return_if_fail (E_IS_WEBKIT_EDITOR (wk_editor));
 
-       g_clear_object (&wk_editor->priv->web_extension);
+       /* The vanished callback can be sometimes called before the appeared
+          callback, in which case it doesn't make sense to unwatch the name. */
+       if (wk_editor->priv->web_extension) {
+               g_clear_object (&wk_editor->priv->web_extension);
 
-       if (wk_editor->priv->web_extension_watch_name_id > 0) {
-               g_bus_unwatch_name (wk_editor->priv->web_extension_watch_name_id);
-               wk_editor->priv->web_extension_watch_name_id = 0;
+               if (wk_editor->priv->web_extension_watch_name_id > 0) {
+                       g_bus_unwatch_name (wk_editor->priv->web_extension_watch_name_id);
+                       wk_editor->priv->web_extension_watch_name_id = 0;
+               }
        }
 }