[gnome-control-center] printers: Fix incorrect g_task_run_in_thread reference usage

[Marek Kašík <mkasik src gnome org>]

commit 172ab6ef6c52d8e79129c011d14c390924f81a86
Author: Robert Ancell <robert ancell canonical com>
Date:   Fri Nov 23 10:54:27 2018 +1300

    printers: Fix incorrect g_task_run_in_thread reference usage
    
    There is a reference held during this call so don't need to
    explicitly unref inside the function.

 panels/printers/pp-host.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/panels/printers/pp-host.c b/panels/printers/pp-host.c
index 6db591d32..ea5e0d16d 100644
--- a/panels/printers/pp-host.c
+++ b/panels/printers/pp-host.c
@@ -749,7 +749,6 @@ _pp_host_get_lpd_devices_thread (GTask        *task,
 
 out:
   g_task_return_pointer (task, devices, (GDestroyNotify) pp_devices_list_free);
-  g_object_unref (task);
 
   g_free (address);
 }
@@ -760,7 +759,7 @@ pp_host_get_lpd_devices_async (PpHost              *host,
                                GAsyncReadyCallback  callback,
                                gpointer             user_data)
 {
-  GTask   *task;
+  g_autoptr(GTask) task = NULL;
 
   task = g_task_new (G_OBJECT (host), cancellable, callback, user_data);
   g_task_run_in_thread (task, _pp_host_get_lpd_devices_thread);