tap: fix the segv

Type: fix

Change-Id: I53cb96950f8658d7159fb0bd8ecfa50b6977e5af
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>
diff --git a/src/vnet/devices/tap/tap.c b/src/vnet/devices/tap/tap.c
index 6ad0177..aa9182a 100644
--- a/src/vnet/devices/tap/tap.c
+++ b/src/vnet/devices/tap/tap.c
@@ -109,8 +109,11 @@
     virtio_vring_free_tx (vm, vif, TX_QUEUE (i));
   /* *INDENT-ON* */
 
-  _IOCTL (vif->tap_fds[0], TUNSETPERSIST, (void *) (uintptr_t) 0);
-  tap_log_dbg (vif, "TUNSETPERSIST: unset");
+  if (vif->tap_fds)
+    {
+      _IOCTL (vif->tap_fds[0], TUNSETPERSIST, (void *) (uintptr_t) 0);
+      tap_log_dbg (vif, "TUNSETPERSIST: unset");
+    }
 error:
   vec_foreach_index (i, vif->tap_fds) close (vif->tap_fds[i]);