http2: set origin name correctly when servername is empty

Fixes: nodejs#39919

lib/internal/http2/core.js

@@ -3098,7 +3098,7 @@ function initializeTLSOptions(options, servername) {
   options.ALPNProtocols = ['h2'];
   if (options.allowHTTP1 === true)
     ArrayPrototypePush(options.ALPNProtocols, 'http/1.1');
-  if (servername !== undefined && options.servername === undefined)
+  if (servername !== undefined && !options.servername)
     options.servername = servername;
   return options;
 }

test/internet/test-http2-https-origin-string-correctness.js

@@ -0,0 +1,42 @@
+'use strict';
+
+// Ref: https://github.com/nodejs/node/issues/39919
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const assert = require('assert');
+const http2 = require('http2');
+
+function _verifyOriginSet(session, originString) {
+  session.once('remoteSettings', () => {
+    assert.strictEqual(typeof session.originSet, 'object');
+    assert.strictEqual(session.originSet.length, 1);
+    assert.strictEqual(session.originSet[0], originString);
+    session.close();
+  });
+  session.once('error', (error) => {
+    assert.strictEqual(error.code, 'ECONNREFUSED');
+    session.close();
+  });
+}
+
+function withServerName() {
+  const session = http2.connect('https://1.1.1.1', { servername: 'cloudflare-dns.com' });
+  _verifyOriginSet(session, 'https://cloudflare-dns.com');
+}
+
+function withEmptyServerName() {
+  const session = http2.connect('https://1.1.1.1', { servername: '' });
+  _verifyOriginSet(session, 'https://1.1.1.1');
+}
+
+function withoutServerName() {
+  const session = http2.connect('https://1.1.1.1');
+  _verifyOriginSet(session, 'https://1.1.1.1');
+}
+
+withServerName();
+withEmptyServerName();
+withoutServerName();