weston: gal2d-renderer: Do not flip buffers if the output damage is empty

There is no need go through all views and copy nothing and flip buffers.

---
 src/gal2d-renderer.c | 3 +++

 1 file changed, 3 insertions(+)

index d2a29ff..1c81287 100644
@@ -943,6 +943,9 @@ gal2d_renderer_repaint_output(struct weston_output *output,

  if (use_output(output) < 0)
  return;
+
+ if (!pixman_region32_not_empty(output_damage))
+ return;

  for (i = 0; i < 2; i++) pixman_region32_union(&go->buffer_damage[i],

2.5.0