[gnome-chess] Never try to kill the same engine process twice

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 28cbad3a1959c8d39ca379a747f9305abc1874f3
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Tue Jan 7 20:29:11 2014 -0600

    Never try to kill the same engine process twice

 src/chess-engine.vala |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/chess-engine.vala b/src/chess-engine.vala
index 536e73e..07ca797 100644
--- a/src/chess-engine.vala
+++ b/src/chess-engine.vala
@@ -113,7 +113,10 @@ public abstract class ChessEngine : Object
         }
 
         if (pid != 0)
+        {
             Posix.kill (pid, Posix.SIGTERM);
+            pid = 0;
+        }
     }
 
     private bool read_cb (IOChannel source, IOCondition condition)