refs #15982 [finc] JS Tree Renderer: fix undefined variable error for empty options

module/finc/src/finc/Hierarchy/TreeRenderer/JSTree.php

@@ -99,7 +99,7 @@ class JSTree extends \VuFind\Hierarchy\TreeRenderer\JSTree
                         ]
                     ];
                 }
-                $cache[$route] = $this->router->fromRoute($route, $params, $options);
+                $cache[$route] = $this->router->fromRoute($route, $params, $options ?? []);
             } elseif ($route == 'parent') {
                 // this is nearly the same as for collections
                 // but links on the record view i.e. record route
@@ -118,7 +118,7 @@ class JSTree extends \VuFind\Hierarchy\TreeRenderer\JSTree
                 }
                 // use route 'record' here to avoid linking to the
                 // collection view
-                $cache[$route] = $this->router->fromRoute('record', $params, $options);
+                $cache[$route] = $this->router->fromRoute('record', $params, $options ?? []);
             } else {
                 $tab = $this->treeRendererConfig->linkedTabDefault ?? 'Description';
                 $params = [