[mutter] native: Return an error if no drm devices are found

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 0fbda366e838dd675022deb383cef9ed5222ce00
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Apr 24 15:15:53 2020 +0200

    native: Return an error if no drm devices are found
    
    Without this, we'll end up segfaulting when trying to log the
    non-existing error.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1217

 src/backends/native/meta-udev.c | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/src/backends/native/meta-udev.c b/src/backends/native/meta-udev.c
index 2f19c8c9c..4cf9e379f 100644
--- a/src/backends/native/meta-udev.c
+++ b/src/backends/native/meta-udev.c
@@ -148,6 +148,13 @@ meta_udev_list_drm_devices (MetaUdev  *udev,
       l = l_next;
     }
 
+  if (!devices)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                   "No DRM devices found");
+      return NULL;
+    }
+
   return devices;
 }