[libadwaita] carousel: Fix crash when attempting to scroll on an empty carousel

[Alexander Mikhaylenko <alexm src gnome org>]

commit edd7216016b62d6c1ca61625af759f15cd680b03
Author: Joshua Lee <lee son wai gmail com>
Date:   Tue Jul 20 01:41:56 2021 +0100

    carousel: Fix crash when attempting to scroll on an empty carousel
    
    If there are no pages in a carousel, abandon the attempt at scrolling through
    it.
    
    Fixes #231

 src/adw-carousel.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/adw-carousel.c b/src/adw-carousel.c
index 3cddcfd9..cf66b82b 100644
--- a/src/adw-carousel.c
+++ b/src/adw-carousel.c
@@ -492,6 +492,9 @@ scroll_cb (AdwCarousel              *self,
   if (!adw_carousel_get_interactive (self))
     return GDK_EVENT_PROPAGATE;
 
+  if (adw_carousel_get_n_pages (self) == 0)
+    return GDK_EVENT_PROPAGATE;
+
   source_device = gtk_event_controller_get_current_event_device (GTK_EVENT_CONTROLLER (controller));
   input_source = gdk_device_get_source (source_device);
   if (input_source == GDK_SOURCE_TOUCHPAD)