Fixes #3730

Add extra check for missing response content and contentType

src/core/components/response-body.jsx

@@ -83,8 +83,12 @@ export default class ResponseBody extends React.Component {
       // Anything else (CORS)
     } else if (typeof content === "string") {
       bodyEl = <HighlightCode value={ content } />
-    } else {
+    } else if ( content.size > 0 ) {
+      // We don't know the contentType, but there was some content returned
       bodyEl = <div>Unknown response type</div>
+    } else {
+      // We don't know the contentType and there was no content returned
+      bodyEl = null
     }
 
     return ( !bodyEl ? null : <div>