Enable the no-typeof-undefined ESLint plugin rule

Please see https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/no-typeof-undefined.md

src/display/fetch_stream.js

@@ -46,7 +46,7 @@ function createHeaders(httpHeaders) {
   const headers = new Headers();
   for (const property in httpHeaders) {
     const value = httpHeaders[property];
-    if (typeof value === "undefined") {
+    if (value === undefined) {
       continue;
     }
     headers.append(property, value);