--- a/src/group_gui.cpp	Sat Aug 04 00:45:53 2007 +0000
+++ b/src/group_gui.cpp	Sat Aug 04 01:25:44 2007 +0000
@@ -780,6 +780,8 @@
 
 void ShowPlayerGroup(PlayerID player, VehicleType vehicle_type)
 {
+	if (!IsValidPlayer(player)) return;
+
 	WindowClass wc;
 
 	switch (vehicle_type) {