check that content type exists before setting it

src/utils/proxies/credentialed.js

@@ -19,7 +19,7 @@ export default async function credentialedProxyHandler(req, res) {
         },
       });
 
-      res.setHeader("Content-Type", contentType);
+      if (contentType) res.setHeader("Content-Type", contentType);
       return res.status(status).send(data);
     }
   }

src/utils/proxies/generic.js

@@ -12,7 +12,7 @@ export default async function genericProxyHandler(req, res) {
       const url = new URL(formatApiCall(widget.type, { endpoint, ...widget }));
       const [status, contentType, data] = await httpProxy(url);
 
-      res.setHeader("Content-Type", contentType);
+      if (contentType) res.setHeader("Content-Type", contentType);
       return res.status(status).send(data);
     }
   }