[evolution/gnome-3-24] AlertBar from ShellContent not freed

[Milan Crha <mcrha src gnome org>]

commit 6634171c3d4ca144a4510a5aba7c3e27370473bb
Author: Milan Crha <mcrha redhat com>
Date:   Tue Jul 11 19:15:05 2017 +0200

    AlertBar from ShellContent not freed
    
    That was a memory leak, but apart of that it could also cause use-after-free
    crash in gtk_widget_get_scale_factor() under _gtk_style_cascade_add_provider()
    called from shell_window_constructed(), when creating a new shell window
    for the second time, with the previous one already closed.

 src/shell/e-shell-content.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/src/shell/e-shell-content.c b/src/shell/e-shell-content.c
index 88a7fe7..662b458 100644
--- a/src/shell/e-shell-content.c
+++ b/src/shell/e-shell-content.c
@@ -150,7 +150,10 @@ shell_content_dispose (GObject *object)
                priv->shell_view = NULL;
        }
 
-       g_clear_object (&priv->alert_bar);
+       if (priv->alert_bar) {
+               gtk_widget_unparent (priv->alert_bar);
+               g_clear_object (&priv->alert_bar);
+       }
 
        /* Chain up to parent's dispose() method. */
        G_OBJECT_CLASS (e_shell_content_parent_class)->dispose (object);
@@ -351,7 +354,7 @@ shell_content_remove (GtkContainer *container,
 
        if (widget == priv->alert_bar) {
                gtk_widget_unparent (priv->alert_bar);
-               priv->alert_bar = NULL;
+               g_clear_object (&priv->alert_bar);
                return;
        }