avf: don't memcpy if adminq output buffer size is 0

Type: fix
Change-Id: I0df14ff87d0bf51eeb392f72434febf6c4a2957a
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/plugins/avf/device.c b/src/plugins/avf/device.c
index 139f1c9..fd17398 100644
--- a/src/plugins/avf/device.c
+++ b/src/plugins/avf/device.c
@@ -485,7 +485,7 @@
       goto done;
     }
 
-  if (d->flags & AVF_AQ_F_BUF)
+  if (out_len && d->flags & AVF_AQ_F_BUF)
     {
       void *buf = ad->arq_bufs + ad->arq_next_slot * AVF_MBOX_BUF_SZ;
       clib_memcpy_fast (out, buf, out_len);