unfortunately I can test this in dev...

static/admin/prefixed-image-widget.js

@@ -1,3 +1,10 @@
+(function waitForCMSAndReact() {
+  if (!(window.CMS && window.React)) {
+    setTimeout(waitForCMSAndReact, 50);
+    return;
+  }
+  const React = window.React;
+
   class PrefixedImageControl extends React.Component {
     openMediaLibrary = () => {
       this.props.mediaLibrary.open({
@@ -45,3 +52,4 @@ window.CMS.registerWidget(
     PrefixedImageWidget.controlComponent,
     PrefixedImageWidget.previewComponent
   );
+})();