Driverhook H_NOTIFY_FAIL: this_player pruefen

Wenn der Client unguenstig disconnected, ist offenbar
tatsaechlich this_player() im Hook weg.

Change-Id: I65e140cd2bb0d5d7d268b38b46db130d223337e2
diff --git a/secure/master.c b/secure/master.c
index 0574cdf..99a4eb6 100644
--- a/secure/master.c
+++ b/secure/master.c
@@ -120,7 +120,7 @@
   // Standard-Fehlermeldung
   //set_driver_hook(H_NOTIFY_FAIL,        "Wie bitte?\n");
   set_driver_hook(H_NOTIFY_FAIL, function string (string cmd, object tp)
-      {if (stringp(cmd=(string)tp->QueryProp(P_DEFAULT_NOTIFY_FAIL)))
+      {if (tp && stringp(cmd=(string)tp->QueryProp(P_DEFAULT_NOTIFY_FAIL)))
          return(cmd);
        return("Wie bitte?\n");});