Patch-Magento_Catalog-0001-Fix-for-5897-getIdentities-relies-on-uninitialized-c.patch

--- a/Block/Product/ProductList/Related.php	2017-10-18 16:31:27.648839713 +0200
+++ b/Block/Product/ProductList/Related.php	2017-10-18 16:34:42.703371653 +0200
@@ -115,6 +115,13 @@
      */
     public function getItems()
     {
+        /**
+         * getIdentities() depends on _itemCollection populated, but it can be empty if the block is hidden
+         * @see https://github.com/magento/magento2/issues/5897
+         */
+        if (is_null($this->_itemCollection)) {
+            $this->_prepareData();
+        }
         return $this->_itemCollection;
     }