tried quickly to fix constant 401 in tests

frontend/src/App.jsx

@@ -117,10 +117,10 @@ const App = (props) => {
 
     fetchData()
 
-    const loginInterval = setInterval(() => {
+    const loginInterval = setInterval(async () => {
       if (!isCustomerReviewPage) {
         try {
-          loginService.login()
+          await loginUser()
         } catch (err) {
           console.log(err)
         }

frontend/src/reducers/actions/userActions.js

@@ -9,8 +9,12 @@ const updateIsInstructor = (user, isInstructor) => ({
 
 export const loginUser = (userCredentials) => {
   return async (dispatch) => {
-    const { user, token } = await loginService.login(userCredentials)
+    if (!userCredentials) {
+      console.warn("Login failed: No credentials given")
+      return
+    }
 
+    const { user, token } = await loginService.login(userCredentials)
     const { isInstructor } = await userService.checkInstructor(token)
 
     dispatch({