Description of problem:

pixbuf module crashes in EL8, debugging shows that gdk pixbuf passes the size_func and the update_func as NULL.

These functions are implemented as an empty implementations https://gitlab.gnome.org/GNOME/gdk-pixbuf/-/blob/master/gdk-pixbuf/gdk-pixbuf-io.c#L1032 :

```
static void
noop_size_notify (gint *width,
gint *height,
gpointer data)
{
}

[...]

static void
noop_updated_notify (GdkPixbuf *pixbuf,
int x,
int y,
int width,
int height,
gpointer user_data)
{
}

static GdkPixbuf *
generic_load_incrementally (GdkPixbufModule *module, FILE *f, GError **error)
{
context = module->begin_load (noop_size_notify, prepared_notify, noop_updated_notify, &pixbuf, error);
```

Version-Release number of selected component (if applicable):

[root@5eea7fe404f1 tests]# rpm -qi gdk-pixbuf2
Name : gdk-pixbuf2
Version : 2.36.12
Release : 5.el8

How reproducible:
Always