[pango/pango2] userface: docs fixup

[Matthias Clasen <matthiasc src gnome org>]

commit fcbc9ecabe305e8bc9b4fef2d12446ab64782c49
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jun 19 07:48:51 2022 -0700

    userface: docs fixup

 pango/pango-userface.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/pango/pango-userface.c b/pango/pango-userface.c
index c5baab60..7e6f702b 100644
--- a/pango/pango-userface.c
+++ b/pango/pango-userface.c
@@ -384,7 +384,7 @@ pango_user_face_class_init (PangoUserFaceClass *class)
  * @user_data: user data that will be assed to the callbacks
  * @destroy: destroy notify for @user_data
  * @name: name for the face
- * @description: (nullable): `PangoFontDescription` for the font
+ * @description: `PangoFontDescription` for the font
  *
  * Creates a new user font face.
  *
@@ -414,6 +414,12 @@ pango_user_face_new (PangoUserFaceGetFontInfoFunc     font_info_func,
   PangoUserFace *self;
   PangoFontFace *face;
 
+  g_return_val_if_fail (font_info_func != NULL, NULL);
+  g_return_val_if_fail (glyph_func != NULL, NULL);
+  g_return_val_if_fail (glyph_info_func != NULL, NULL);
+  g_return_val_if_fail (name != NULL, NULL);
+  g_return_val_if_fail (description != NULL, NULL);
+
   self = g_object_new (PANGO_TYPE_USER_FACE, NULL);
 
   self->font_info_func = font_info_func;