[mutter] cogl/renderer: Set error in dmabuf constructor fallback

[Jonas Ådahl <jadahl src gnome org>]

commit 7d822459de31bdf7239fd83d67b19ae2961ef747
Author: Jonas Ådahl <jadahl gmail com>
Date:   Tue Sep 8 14:22:33 2020 +0200

    cogl/renderer: Set error in dmabuf constructor fallback
    
    When the CoglRenderer didn't set the DMA buffer constructor vfunc, we
    return NULL. What we didn't do was set the error, meaning the caller
    would crash if it tried to look up why DMA buffer construction failed.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1430

 cogl/cogl/cogl-renderer.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/cogl/cogl/cogl-renderer.c b/cogl/cogl/cogl-renderer.c
index 3dc22c1901..b0386fa51e 100644
--- a/cogl/cogl/cogl-renderer.c
+++ b/cogl/cogl/cogl-renderer.c
@@ -31,6 +31,7 @@
 
 #include "cogl-config.h"
 
+#include <gio/gio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -768,5 +769,8 @@ cogl_renderer_create_dma_buf (CoglRenderer  *renderer,
   if (winsys->renderer_create_dma_buf)
     return winsys->renderer_create_dma_buf (renderer, width, height, error);
 
+  g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
+               "CoglRenderer doesn't support creating DMA buffers");
+
   return NULL;
 }