few fixes for react errors

frontend/src/App.js

 import React from 'react';
 import './App.scss';
-import { BrowserRouter as Router, Switch, Route, Link } from "react-router-dom";
+import { BrowserRouter as Router, Switch, Route } from "react-router-dom";
 import Startseite from './components/startseite/Startseite';
 import BTMBuch from './components/btmbuch/BTMBuch';
 import ApothekeEinstellungen from './components/apotheke/einstellungen/ApothekeEinstellungen';

frontend/src/components/apotheke/ApothekeBtmList.js

@@ -57,8 +57,9 @@ function ApothekeBtmList(props) {
           } else if (val.btm.name.toLowerCase().includes(input.toLowerCase())){
               return val;
           }
+          return null;
         })
-        .map((btm, key) => (
+        .map((btm) => (
           <BuchungTabelle {...props} btm={btm} />
         ))}
     </div>

frontend/src/components/apotheke/ApothekenDetails.js

 import React, { useEffect, useState } from "react";
-import { useParams, Link  } from 'react-router-dom';
+import { Link  } from 'react-router-dom';
 import { Button } from "react-bootstrap";
 import NeuesBtmModal from "../btmbuch/NeuesBtmModal";
 import "../../App.scss";

frontend/src/components/btmbuch/BuchungTabelle.js

@@ -10,23 +10,12 @@ import TableBody from '@material-ui/core/TableBody';
 import NeueBuchungModal from "./NeueBuchungModal";
 import UpdateBuchungModal from "../../modals/UpdateBuchungModal";
 import DeleteModal from "../../modals/DeleteModal";
-import { makeStyles } from '@material-ui/core/styles';
 import TablePagination from '@material-ui/core/TablePagination';
 
-const useStyles = makeStyles({
-  root: {
-    width: '100%',
-  },
-  container: {
-    maxHeight: 440,
-  },
-});
-
 function BuchungTabelle(props) {
   let { btm } = props;
   const { apoId } = useParams();
 
-  const classes = useStyles();
   const [page, setPage] = React.useState(0);
   const [rowsPerPage, setRowsPerPage] = React.useState(10);
 

frontend/src/modals/ApothekeRegisterModal.js

-import React, { useEffect, useState } from "react";
-import { useParams } from 'react-router-dom';
+import React, { useState } from "react";
 import { makeStyles, useTheme } from "@material-ui/core/styles";
-import { Modal, Button, Form, Row, Col } from "react-bootstrap";
+import { Modal, Button, Form, Col } from "react-bootstrap";
 import { useForm } from "./useForm";
 import MobileStepper from "@material-ui/core/MobileStepper";
 import KeyboardArrowLeft from "@material-ui/icons/KeyboardArrowLeft";
@@ -297,8 +296,8 @@ function ApothekeRegisterModal(props) {
           nextButton={
             <Button
               size="small"
-              type={activeStep == 1 ? "submit" : "button"}
-              onClick={activeStep == 0 ? handleNext : null}
+              type={activeStep === 1 ? "submit" : "button"}
+              onClick={activeStep === 0 ? handleNext : null}
               disabled={activeStep === 2}
             >
               {activeStep === 1 ? 'Registrien' : 'Weiter'}
@@ -308,7 +307,7 @@ function ApothekeRegisterModal(props) {
           backButton={
             <Button
               size="small"
-              type={activeStep == 1 ? "submit" : "button"}
+              type={activeStep === 1 ? "submit" : "button"}
               onClick={handleBack}
               disabled={activeStep === 0}
             >

frontend/src/modals/UpdateBuchungModal.js

-import React,{useEffect} from 'react';
+import React from 'react';
 import { Modal, Button, Form, Row, Col } from 'react-bootstrap';
 import { useSnackbar } from 'notistack';
 import { useParams } from 'react-router-dom';

frontend/src/user/UserDetails.js

@@ -5,7 +5,7 @@ import UserDetailsUpdateModal from '../modals/UserDetailsUpdateModal';
 
 function UserDetails(props) {
     //eslint disable-next-line
-   const {rolle, vorname, name, nutzername, aktiv} = props.user;
+   const {rolle, nutzername } = props.user;
    const [showUserSettings, setShowUserSettings] = useState(false);
 
    var allRoles = {