Error #1 FF

[Vue warn]: Error in mounted hook: "TypeError: slug is undefined"

found in

---> <BackendComponentDocumentHeader>
       <BackendComponentDocument>
         <CmsEditorComponentPageEditor>
           <BackendComponentTabs>
             <BackendComponentSplitter>
               <EditorComponentApplication>
                 <Root> storm-min.js:2644:466
    warn https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2644
    logError https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2772
    globalHandleError https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2771
    handleError https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2767
    invokeWithErrorHandling https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2768
    callHook https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2985
    insert https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2880
    invokeInsertHook https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:3193
    patch https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:3217
    _update https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2957
    updateComponent https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2968
    get https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:3004
    run https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:3007
    flushSchedulerQueue https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2992
    nextTick https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2776
    flushCallbacks https://tennisv2.ctrl-felix.de/modules/system/assets/ui/storm-min.js?v=1aec7fa3:2774