Do not show slots conditional order types when slots not enabled in UI

src/order_gui.cpp

@@ -2101,11 +2101,15 @@ public:
 				break;
 
 			case WID_O_COND_VARIABLE: {
+				const OrderConditionVariable ocv = this->vehicle->GetOrder(this->OrderGetSel())->GetConditionVariable();
 				DropDownList list;
 				for (uint i = 0; i < lengthof(_order_conditional_variable); i++) {
+					if (ocv != _order_conditional_variable[i]) {
+						if ((_order_conditional_variable[i] == OCV_TRAIN_IN_SLOT || _order_conditional_variable[i] == OCV_SLOT_OCCUPANCY) && !_settings_client.gui.show_adv_tracerestrict_features) continue;
+					}
 					list.emplace_back(new DropDownListStringItem(STR_ORDER_CONDITIONAL_LOAD_PERCENTAGE + _order_conditional_variable[i], _order_conditional_variable[i], false));
 				}
-				ShowDropDownList(this, std::move(list), this->vehicle->GetOrder(this->OrderGetSel())->GetConditionVariable(), WID_O_COND_VARIABLE);
+				ShowDropDownList(this, std::move(list), ocv, WID_O_COND_VARIABLE);
 				break;
 			}