del

public/react/src/modules/courses/exercise/new/NullEditor.js

@@ -196,6 +196,7 @@ class NullEditor extends Component{
   }
   
   onAnswerChange = (index, itemIndex, val) => {
+    if (this.state.standard_answers[index]) {
     this.setState(
         (prevState) => ({ 
           standard_answers : update(prevState.standard_answers
@@ -203,6 +204,7 @@ class NullEditor extends Component{
         })
       )
     }
+  }
   addChildAnswer = (index) => {
     this.setState(
         (prevState) => ({