fix script error in power library when a foundry (not really a consumer) is removed

planet/Objects.ocd/Libraries.ocd/Structures.ocd/Power.ocd/Consumer.ocd/Script.c

@@ -136,6 +136,8 @@ protected func Initialize()
 // a consumer anymore, it must always be unregistered from the power network.
 protected func Destruction()
 {
+	// Only unregister if this object actually is a consumer.
+	if (IsPowerConsumer())
 		UnregisterPowerRequest();
 	return _inherited(...);
 }