fix(Menu): Fix crash in menu referencing invalid array index (#10153)

* Fix crash in menu

* Update code best on review feedback

* fix linting

Author: jamestalton

packages/react-core/src/components/Menu/Menu.tsx

@@ -156,8 +156,11 @@ class MenuBase extends React.Component<MenuProps, MenuState> {
       this.setState({ transitionMoveTarget: null });
     } else {
       const nextMenu = current.querySelector('#' + this.props.activeMenu) || current || null;
-      const nextMenuChildren = Array.from(nextMenu.getElementsByTagName('UL')[0].children);
-
+      const nextMenuLists = nextMenu.getElementsByTagName('UL');
+      if (nextMenuLists.length === 0) {
+        return;
+      }
+      const nextMenuChildren = Array.from(nextMenuLists[0].children);
       if (!this.state.currentDrilldownMenuId || nextMenu.id !== this.state.currentDrilldownMenuId) {
         this.setState({ currentDrilldownMenuId: nextMenu.id });
       } else {
@@ -167,7 +170,6 @@ class MenuBase extends React.Component<MenuProps, MenuState> {
       const nextTarget = nextMenuChildren.filter(
         (el) => !(el.classList.contains('pf-m-disabled') || el.classList.contains(styles.divider))
       )[0].firstChild;
-
       (nextTarget as HTMLElement).focus();
       (nextTarget as HTMLElement).tabIndex = 0;
     }