(svn r6228) -Fix: redrawing an empty list of shared vehicles will now close the window

Since the order is no more, the player will not need that particular window anymore
	this could happen if the player opened the window and then sold all the vehicles (or crashed them)
	A crash could happen if a new order gets the same (now freed) OrderID and the vehicle using it is not of the same type as the window expect

vehicle_gui.c

@@ -1244,6 +1244,18 @@ void PlayerVehWndProc(Window *w, WindowEvent *e)
 			switch (window_type) {
 				case VLW_SHARED_ORDERS:
 					/* Shared Orders */
+					if (vl->list_length == 0) {
+						/* The list is empty, so the last vehicle is sold or crashed */
+						/* Delete the window because the order is now not in use anymore */
+						switch (vehicle_type) {
+							case VEH_Train:    DeleteWindowById(WC_TRAINS_LIST,   w->window_number); break;
+							case VEH_Road:     DeleteWindowById(WC_ROADVEH_LIST,  w->window_number); break;
+							case VEH_Ship:     DeleteWindowById(WC_SHIPS_LIST,    w->window_number); break;
+							case VEH_Aircraft: DeleteWindowById(WC_AIRCRAFT_LIST, w->window_number); break;
+							default: NOT_REACHED(); break;
+						}
+						return;
+					}
 					SetDParam(0, w->vscroll.count);
 					w->widget[1].unkA  = STR_VEH_WITH_SHARED_ORDERS_LIST;
 					w->widget[9].unkA  = STR_EMPTY;