fixed undefined

Author: leventeBajczi

frontend/src/App.jsx

@@ -7,7 +7,7 @@ import FolderOpenIcon from '@mui/icons-material/FolderOpen'
 import ExampleTree from './components/ExampleTree'
 import axios from 'axios'
 
-const API_ROOT = import.meta.env.VITE_API_ROOT + '/' || ''
+const API_ROOT = import.meta.env.VITE_API_ROOT ? import.meta.env.VITE_API_ROOT + '/' : ''
 
 export default function App() {
   const [examples, setExamples] = useState([])