Prevent RequestBody from accessing a media type that ceased to exist

src/core/components/content-type.jsx

@@ -27,6 +27,16 @@ export default class ContentType extends React.Component {
     }
   }
 
+  componentWillReceiveProps(nextProps) {
+    if(!nextProps.contentTypes || !nextProps.contentTypes.size) {
+      return
+    }
+
+    if(!nextProps.contentTypes.includes(nextProps.value)) {
+      nextProps.onChange(nextProps.contentTypes.first())
+    }
+  }
+
   onChangeWrapper = e => this.props.onChange(e.target.value)
 
   render() {

src/core/plugins/oas3/components/request-body.jsx

@@ -22,6 +22,10 @@ const RequestBody = ({
 
   const mediaTypeValue = requestBodyContent.get(contentType)
 
+  if(!mediaTypeValue) {
+    return null
+  }
+
   return <div>
     { requestBodyDescription &&
       <Markdown source={requestBodyDescription} />