[gnome-settings-daemon] smartcard: Fix a g_task_return_error(task, NULL) call

[Bastien Nocera <hadess src gnome org>]

commit b719bc0999998508b14ad8b05412fd7431bcd4f3
Author: Philip Withnall <withnall endlessm com>
Date:   Thu Jan 19 20:24:28 2017 +0000

    smartcard: Fix a g_task_return_error(task, NULL) call
    
    It’s possible for activate_all_drivers_async_finish() to return FALSE
    without an error set, in the case that there were no drivers to activate
    (but there were no errors either).
    
    Fix it to return a new error code
    (GSD_SMARTCARD_MANAGER_ERROR_NO_DRIVERS) in that case, to preserve the
    invariant that a FALSE return value means an error, thus fixing a
    warning I saw in my journal:
       gnome-settings-[641]: g_task_return_error: assertion 'error != NULL' failed
    
    https://bugzilla.gnome.org/show_bug.cgi?id=777508

 plugins/smartcard/gsd-smartcard-manager.c |    6 +++++-
 plugins/smartcard/gsd-smartcard-manager.h |    3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/plugins/smartcard/gsd-smartcard-manager.c b/plugins/smartcard/gsd-smartcard-manager.c
index 7fef9c5..a624542 100644
--- a/plugins/smartcard/gsd-smartcard-manager.c
+++ b/plugins/smartcard/gsd-smartcard-manager.c
@@ -511,7 +511,9 @@ try_to_complete_all_drivers_activation (GTask *task)
         if (operation->activated_drivers_count > 0)
                 g_task_return_boolean (task, TRUE);
         else
-                g_task_return_boolean (task, FALSE);
+                g_task_return_new_error (task, GSD_SMARTCARD_MANAGER_ERROR,
+                                         GSD_SMARTCARD_MANAGER_ERROR_NO_DRIVERS,
+                                         "No smartcards exist to be activated.");
 
         g_object_unref (task);
 }
@@ -581,6 +583,8 @@ activate_all_drivers_async (GsdSmartcardManager *self,
         try_to_complete_all_drivers_activation (task);
 }
 
+/* Will error with %GSD_SMARTCARD_MANAGER_ERROR_NO_DRIVERS if there were no
+ * drivers to activate.. */
 static gboolean
 activate_all_drivers_async_finish (GsdSmartcardManager  *self,
                                    GAsyncResult         *result,
diff --git a/plugins/smartcard/gsd-smartcard-manager.h b/plugins/smartcard/gsd-smartcard-manager.h
index 935c35d..13eb403 100644
--- a/plugins/smartcard/gsd-smartcard-manager.h
+++ b/plugins/smartcard/gsd-smartcard-manager.h
@@ -60,7 +60,8 @@ typedef enum
          GSD_SMARTCARD_MANAGER_ERROR_LOADING_DRIVER,
          GSD_SMARTCARD_MANAGER_ERROR_WATCHING_FOR_EVENTS,
          GSD_SMARTCARD_MANAGER_ERROR_REPORTING_EVENTS,
-         GSD_SMARTCARD_MANAGER_ERROR_FINDING_SMARTCARD
+         GSD_SMARTCARD_MANAGER_ERROR_FINDING_SMARTCARD,
+         GSD_SMARTCARD_MANAGER_ERROR_NO_DRIVERS,
 } GsdSmartcardManagerError;
 
 GType                   gsd_smartcard_manager_get_type    (void);