fix: confirmation window is displayed after save for dropdown

"No answer specified" confirmation window is displayed all the
time after second save for dropdown.

src/editors/containers/ProblemEditor/components/EditProblemView/hooks.js

@@ -94,7 +94,7 @@ export const checkForNoAnswers = ({ openSaveWarningModal, problem }) => {
     let correctAnswer;
     answers.forEach(answer => {
       if (answer.correct) {
-        const title = simpleTextAreaProblems.includes(problemType) ? answer.title : answerTitles[answer.id];
+        const title = simpleTextAreaProblems.includes(problemType) ? answer.title.toString() : answerTitles[answer.id];
         if (title.length > 0) {
           correctAnswer = true;
         }