MC-15533: Product attribute template incorrectly handles data

Author: nathanjosiah

app/code/Magento/Catalog/view/frontend/templates/product/view/attribute.phtml

@@ -15,6 +15,11 @@
 <?php
 $_helper = $this->helper('Magento\Catalog\Helper\Output');
 $_product = $block->getProduct();
+
+if (!$_product instanceof \Magento\Catalog\Model\Product) {
+    return;
+}
+
 $_call = $block->getAtCall();
 $_code = $block->getAtCode();
 $_className = $block->getCssClass();

dev/tests/integration/testsuite/Magento/Catalog/Block/Product/View/DescriptionTest.php

@@ -0,0 +1,51 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+namespace Magento\Catalog\Block\Product;
+
+use Magento\Framework\Registry;
+use Magento\TestFramework\Helper\Bootstrap;
+
+/**
+ * @magentoAppArea frontend
+ */
+class DescriptionTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @var View\Description
+     */
+    private $block;
+
+    /**
+     * @var Registry
+     */
+    private $registry;
+
+    protected function setUp()
+    {
+        $objectManager = Bootstrap::getObjectManager();
+        $this->block = $objectManager->create(View\Description::class, [
+            'data' => [
+                'template' => 'Magento_Catalog::product/view/attribute.phtml'
+            ]
+        ]);
+
+        $this->registry = $objectManager->get(Registry::class);
+        $this->registry->unregister('product');
+    }
+
+    public function testGetProductWhenNoProductIsRegistered()
+    {
+        $html = $this->block->toHtml();
+        $this->assertEmpty($html);
+    }
+
+    public function testGetProductWhenInvalidProductIsRegistered()
+    {
+        $this->registry->register('product', new \stdClass());
+        $html = $this->block->toHtml();
+        $this->assertEmpty($html);
+    }
+}