(svn r23484) -Fix [FS#4770]: in case you already have orders, ignore the vehicles when adding an extra order

src/window_gui.h

@@ -667,8 +667,9 @@ public:
 	/**
 	 * The user clicked on a vehicle while HT_VEHICLE has been set.
 	 * @param v clicked vehicle. It is guaranteed to be v->IsPrimaryVehicle() == true
+	 * @return True if the click is handled, false if it is ignored.
 	 */
-	virtual void OnVehicleSelect(const struct Vehicle *v) {}
+	virtual bool OnVehicleSelect(const struct Vehicle *v) { return false; }
 
 	/**
 	 * The user cancelled a tile highlight mode that has been set.