message: Added missing null check
  Fixes a possible nullpointer exception when used as a controlled component.
diff: @@ -142,8 +142,9 @@ export class VariableEditor extends React.Component {
  this.props.value !== prevProps.value &&
  this.props.value !== this.cachedValue
  ) {
  - this.cachedValue = this.props.value;
  - this.editor.setValue(this.props.value);
  + const thisValue = this.props.value || '';
  + this.cachedValue = thisValue;
  + this.editor.setValue(thisValue);
  }
  this.ignoreChangeEvent = false;
  }
  