[bugfix] Add style={{ display }} back to CustomElement so that custom left panel can be shown and hidden correctly. However if this.props.display is not defined we don't want to set inline display to 'flex'. Doing that will force customElement in the header always to visible

Author: ZhijieZhang

src/components/CustomElement/CustomElement.js

@@ -13,6 +13,7 @@ class CustomElement extends React.PureComponent {
     dataElement: PropTypes.string,
     display: PropTypes.string,
     render: PropTypes.func.isRequired,
+    mediaQueryClassName: PropTypes.string
   }
 
   constructor(props) {
@@ -62,6 +63,7 @@ class CustomElement extends React.PureComponent {
         className={[className, mediaQueryClassName].join(' ').trim()}
         ref={this.elementWrapper} 
         data-element={dataElement}
+        style={{ display }}
       >
         {this.state.isRenderingReactComponent &&
           render()