[gcompris] minor: no more crash if gnuchess is not found.

[Bruno Coudoin <bcoudoin src gnome org>]

commit 65688d5dc096fee65bf311e8f5bcf6a703733b7f
Author: Bruno Coudoin <bruno coudoin free fr>
Date:   Thu May 17 20:25:33 2012 +0200

    minor: no more crash if gnuchess is not found.

 src/chess_computer-activity/chess.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/src/chess_computer-activity/chess.c b/src/chess_computer-activity/chess.c
index 7a3e4fa..07b3bf1 100644
--- a/src/chess_computer-activity/chess.c
+++ b/src/chess_computer-activity/chess.c
@@ -352,7 +352,8 @@ static void end_board ()
   info_item     = NULL;
 
 
-  engine_local_destroy(gnuchess_pid);
+  if ( gnuchess_pid )
+    engine_local_destroy(gnuchess_pid);
 }
 
 /* ======================================= */
@@ -1065,7 +1066,7 @@ static void
 engine_local_destroy (GPid gnuchess_pid)
 {
 
-  g_warning("engine_local_destroy () \n");
+  g_warning("engine_local_destroy (%d) \n", gnuchess_pid);
   write_child (write_chan, "quit\n");
 
   g_source_remove(read_cb);