[gtk/bilelmoussaoui/g-i] gtk: mark few GtkFileChooser functions as nullable - get_file, if no file is selected returns a NULL

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit afeb7f668bc63701698a0cfb08d37df88b089acc
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Sat Jan 1 19:11:10 2022 +0100

    gtk: mark few GtkFileChooser functions as nullable
    - get_file, if no file is selected returns a NULL
    - get_id, if the interface doesn't implement such function returns NULL

 gtk/gtkfilechooser.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkfilechooser.c b/gtk/gtkfilechooser.c
index c472e115db..78cfdb1001 100644
--- a/gtk/gtkfilechooser.c
+++ b/gtk/gtkfilechooser.c
@@ -523,7 +523,7 @@ gtk_file_chooser_set_file (GtkFileChooser  *chooser,
  * If the file chooser is in folder mode, this function returns
  * the selected folder.
  *
- * Returns: (transfer full): a selected `GFile`. You own the
+ * Returns: (transfer full) (nullable): a selected `GFile`. You own the
  *   returned file; use g_object_unref() to release it.
  */
 GFile *
@@ -794,7 +794,7 @@ gtk_file_chooser_set_choice (GtkFileChooser  *chooser,
  *
  * Gets the currently selected option in the 'choice' with the given ID.
  *
- * Returns: the ID of the currently selected option
+ * Returns: (nullable): the ID of the currently selected option
  */
 const char *
 gtk_file_chooser_get_choice (GtkFileChooser  *chooser,