fix for React StrictMode

client/src/App.tsx

@@ -44,7 +44,7 @@ function App() {
   if (finished) {
     mainComponent = <GoodBye message={conclusion} />
   } else if (curLevel > 0) {
-    mainComponent = <Level nbLevels={nbLevels} level={curLevel} setCurLevel={setCurLevel} setLevelTitle={setLevelTitle} setFinished={setFinished}/>
+    mainComponent = <Level nbLevels={5} level={curLevel} setCurLevel={setCurLevel} setLevelTitle={setLevelTitle} setFinished={setFinished}/>
   } else {
     mainComponent = <Welcome setNbLevels={setNbLevels} startGame={startGame} setConclusion={setConclusion}/>
   }

client/src/components/Level.tsx

@@ -99,6 +99,8 @@ function Level({ nbLevels, level, setCurLevel, setLevelTitle, setFinished }: Lev
     setEditor(editor)
     setInfoProvider(infoProvider)
     setInfoviewApi(infoviewApi)
+
+    return () => { editor.dispose() }
   }, [])
 
   // The next function will be called when the level changes
@@ -129,40 +131,12 @@ function Level({ nbLevels, level, setCurLevel, setLevelTitle, setFinished }: Lev
     }
   }, [editor, level, leanClient])
 
-  function sendTactic(input) {
-    leanClient.sendRequest("runTactic", {tactic: input}).then(processResponse);
-    setLastTactic(input);
-    setHistory(history.concat([input]));
-  }
-
-  function undo() {
-    if (errors.length === 0) {
-      leanClient.sendRequest('undo', {}).then(processResponse);
-    }
-    if (history.length > 1) {
-      setLastTactic(history[history.length - 1]);
-    } else {
-      setLastTactic("");
-    };
-    setErrors([]);
-    setHistory(history.slice(0, -1));
-  }
-
   function loadLevel(index) {
     setCompleted(false)
     setHistory([])
     setCurLevel(index)
   }
 
-  function closeMessage() {
-    setMessageOpen(false)
-  }
-
-  function finishGame() {
-    setLevelTitle("")
-    setFinished(true)
-  }
-
   return (
     <Grid className="level" container sx={{ mt: 3, ml: 1, mr: 1 }} columnSpacing={{ xs: 1, sm: 2, md: 3 }}>
       <Grid xs={4} className="doc-panel">