[gnome-control-center] object-storage: Check for cancellation before resulting in assert failure

[Robert Ancell <rancell src gnome org>]

commit d7857c113a81554271445b2368742cc3e767aa02
Author: Andrea Azzarone <andrea azzarone canonical com>
Date:   Tue Sep 25 17:12:18 2018 +0200

    object-storage: Check for cancellation before resulting in assert failure
    
    As per doumentation: "It is a programming error to create an identical proxy
    while asynchronously creating one. Not cancelling this operation will result in
    an assertion failure when calling cc_object_storage_create_dbus_proxy_finish()."
    In order to fullfill the second part we need to check for errors (including
    cancellation ones) before we generate an assertion failure.
    
    Fixes: https://gitlab.gnome.org/GNOME/gnome-control-center/issues/158

 shell/cc-object-storage.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)
---
diff --git a/shell/cc-object-storage.c b/shell/cc-object-storage.c
index 46038cc34..3e3ab4d9a 100644
--- a/shell/cc-object-storage.c
+++ b/shell/cc-object-storage.c
@@ -363,6 +363,16 @@ cc_object_storage_create_dbus_proxy_finish (GAsyncResult  *result,
 
   task_data = g_task_get_task_data (task);
 
+  /* Retrieve the newly created proxy */
+  proxy = g_task_propagate_pointer (task, &local_error);
+
+  /* If the proxy is not cached, do the normal caching routine */
+  if (local_error)
+    {
+      g_propagate_error (error, g_steal_pointer (&local_error));
+      return NULL;
+    }
+
   key = g_strdup_printf ("CcObjectStorage::dbus-proxy(%s,%s,%s)",
                          task_data->name,
                          task_data->path,
@@ -379,16 +389,6 @@ cc_object_storage_create_dbus_proxy_finish (GAsyncResult  *result,
   g_assert (task_data != NULL);
   g_assert (task_data->cached == cc_object_storage_has_object (key));
 
-  /* Retrieve the newly created proxy */
-  proxy = g_task_propagate_pointer (task, &local_error);
-
-  /* If the proxy is not cached, do the normal caching routine */
-  if (local_error)
-    {
-      g_propagate_error (error, g_steal_pointer (&local_error));
-      return NULL;
-    }
-
   /* If the proxy is already cached, destroy the newly created and used the cached proxy
    * instead.
    */