Copter: fence.init() was getting called even when AC_FENCE was DISABLED

ArduCopter/system.cpp

@@ -69,8 +69,10 @@ void Copter::init_ardupilot()
     g2.gripper.init();
 #endif
 
+#if AC_FENCE == ENABLED
     fence.init();
-
+#endif
+    
     // init winch and wheel encoder
     winch_init();