[vte] pty: Allow null callback for spawn_async

[Christian Persch <chpe src gnome org>]

commit e56d624372e69facd9f601fae339bae1712ac8b1
Author: Christian Persch <chpe src gnome org>
Date:   Wed Sep 30 21:07:36 2020 +0200

    pty: Allow null callback for spawn_async
    
    Continued from https://gitlab.gnome.org/GNOME/vte/-/issues/286

 src/vtepty.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/src/vtepty.cc b/src/vtepty.cc
index 4705ff9c..128c0215 100644
--- a/src/vtepty.cc
+++ b/src/vtepty.cc
@@ -735,6 +735,8 @@ _vte_pty_check_envv(char const* const* strv) noexcept
  * @child_setup_data_destroy: (destroy child_setup_data): a #GDestroyNotify for @child_setup_data, or %NULL
  * @timeout: a timeout value in ms, -1 for the default timeout, or G_MAXINT to wait indefinitely
  * @cancellable: (allow-none): a #GCancellable, or %NULL
+ * @callback: (nullable) (scope async): a #GAsyncReadyCallback, or %NULL
+ * @user_data: (closure callback): user data for @callback
  *
  * Starts the specified command under the pseudo-terminal @pty.
  * The @argv and @envv lists should be %NULL-terminated.
@@ -804,7 +806,6 @@ try
         g_return_if_fail(!child_setup_data_destroy || child_setup_data);
         g_return_if_fail(timeout >= -1);
         g_return_if_fail(cancellable == nullptr || G_IS_CANCELLABLE (cancellable));
-        g_return_if_fail(callback);
 
         /* These are ignored or need not be passed since the behaviour is the default */
         g_warn_if_fail((spawn_flags & ignored_spawn_flags()) == 0);
@@ -853,6 +854,8 @@ catch (...)
  * @child_setup_data_destroy: (destroy child_setup_data): a #GDestroyNotify for @child_setup_data, or %NULL
  * @timeout: a timeout value in ms, -1 for the default timeout, or G_MAXINT to wait indefinitely
  * @cancellable: (allow-none): a #GCancellable, or %NULL
+ * @callback: (nullable) (scope async): a #GAsyncReadyCallback, or %NULL
+ * @user_data: (closure callback): user data for @callback
  *
  * Like vte_pty_spawn_with_fds_async(), except that this function does not
  * allow passing file descriptors to the child process. See vte_pty_spawn_with_fds_async()