Fixes indexed classed handle resource (#899)

Nothing in WPILib uses it, so it was not tested

hal/src/test/native/cpp/handles/HandleTests.cpp

@@ -0,0 +1,28 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "HAL/HAL.h"
+#include "HAL/handles/IndexedClassedHandleResource.h"
+#include "gtest/gtest.h"
+
+#define HAL_TestHandle HAL_Handle
+
+namespace {
+class MyTestClass {};
+}  // namespace
+
+namespace hal {
+TEST(HandleTests, ClassedHandleTest) {
+  hal::IndexedClassedHandleResource<HAL_TestHandle, MyTestClass, 8,
+                                    HAL_HandleEnum::Vendor>
+      testClass;
+  int32_t status = 0;
+  testClass.Allocate(0, std::make_unique<MyTestClass>(), &status);
+  EXPECT_EQ(0, status);
+}
+
+}  // namespace hal