[gtk/wip/chergert/fix-unused] snapshot: fix warning when asserts are disabled

[Christian Hergert <chergert src gnome org>]

commit c90ffc7363a85e9cb7e8ac8c0fd6d5cef0f5d008
Author: Christian Hergert <chergert redhat com>
Date:   Wed Feb 10 16:03:50 2021 -0800

    snapshot: fix warning when asserts are disabled

 gtk/gtksnapshot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/gtksnapshot.c b/gtk/gtksnapshot.c
index e01ce5ec68..008dd108e4 100644
--- a/gtk/gtksnapshot.c
+++ b/gtk/gtksnapshot.c
@@ -1586,7 +1586,7 @@ void
 gtk_snapshot_gl_shader_pop_texture (GtkSnapshot *snapshot)
 {
   GtkSnapshotState *state = gtk_snapshot_get_current_state (snapshot);
-  GskRenderNode *node;
+  G_GNUC_UNUSED GskRenderNode *node;
 
   if (state->collect_func != gtk_snapshot_collect_gl_shader_texture)
     {