[retro-gtk] retro-pa-player: Don't try to play audio if there are no samples

[Adrien Plazas <aplazas src gnome org>]

commit a1553e5b288a43d38df7a0536eac04aa0719cc56
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Mon Feb 3 18:43:52 2020 +0500

    retro-pa-player: Don't try to play audio if there are no samples
    
    Fix errors in libretro OpenGL test cores.

 retro-gtk/retro-pa-player.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/retro-gtk/retro-pa-player.c b/retro-gtk/retro-pa-player.c
index 4873fe0..488e874 100644
--- a/retro-gtk/retro-pa-player.c
+++ b/retro-gtk/retro-pa-player.c
@@ -159,6 +159,9 @@ on_iterated (RetroCore     *core,
   if (retro_core_is_running_ahead (self->core))
     return;
 
+  if (self->buffer->len == 0)
+    return;
+
   sample_rate = retro_core_get_sample_rate (self->core);
   speed_rate = retro_core_get_speed_rate (self->core);