Fix another potential audio output dead lock

src/audio_output/output.c

@@ -336,6 +336,14 @@ aout_buffer_t * aout_OutputNextBuffer( aout_instance_t * p_aout,
 
     p_aout->output.b_starving = 0;
 
+    p_aout->output.fifo.p_first = p_buffer->p_next;
+    if ( p_buffer->p_next == NULL )
+    {
+        p_aout->output.fifo.pp_last = &p_aout->output.fifo.p_first;
+    }
+
+    aout_unlock_output_fifo( p_aout );
+
     if ( !b_can_sleek &&
           ( (p_buffer->i_pts - start_date > AOUT_PTS_TOLERANCE)
              || (start_date - p_buffer->i_pts > AOUT_PTS_TOLERANCE) ) )
@@ -358,12 +366,5 @@ aout_buffer_t * aout_OutputNextBuffer( aout_instance_t * p_aout,
         aout_unlock_input_fifos( p_aout );
     }
 
-    p_aout->output.fifo.p_first = p_buffer->p_next;
-    if ( p_buffer->p_next == NULL )
-    {
-        p_aout->output.fifo.pp_last = &p_aout->output.fifo.p_first;
-    }
-
-    aout_unlock_output_fifo( p_aout );
     return p_buffer;
 }