fix text editor placeholder

Author: nicolaskruchten

src/components/fields/TextEditor.js

@@ -2,6 +2,7 @@ import Field from './Field';
 import React, {Component} from 'react';
 import PropTypes from 'prop-types';
 import {connectToContainer} from 'lib';
+import nestedProperty from 'plotly.js/src/lib/nested_property';
 import LaTeX from '../widgets/text_editors/LaTeX';
 import RichText from '../widgets/text_editors/RichText';
 import MultiFormat from '../widgets/text_editors/MultiFormat';
@@ -24,7 +25,7 @@ class UnconnectedTextEditor extends Component {
     let fullValue = this.props.fullValue;
 
     let placeholder;
-    if (multiValued || (fullValue && (!container || !container[attr]))) {
+    if (multiValued || (fullValue && (!container || !nestedProperty(container, attr)))) {
       placeholder = fullValue;
       fullValue = '';
     }