Do not allow nullable arrays, which were not correctly implemented

Nullable arrays, which are not used anywhere, were marshalled the same
way as an empty non-null array. The demarshalling logic did not
recognize anything as a null array. Given this, it seems better to just
explicitly not support it.

Fixes https://gitlab.freedesktop.org/wayland/wayland/-/issues/306.

Signed-off-by: Ian Douglas Scott <idscott@system76.com>

src/scanner.c

@@ -411,11 +411,10 @@ static bool
 is_nullable_type(struct arg *arg)
 {
 	switch (arg->type) {
-	/* Strings, objects, and arrays are possibly nullable */
+	/* Strings and objects are possibly nullable */
 	case STRING:
 	case OBJECT:
 	case NEW_ID:
-	case ARRAY:
 		return true;
 	default:
 		return false;