doc: add try/catch in http2 respondWithFile example

PR-URL: #38410
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/http2.md

@@ -1669,10 +1669,17 @@ server.on('stream', (stream) => {
   }
 
   function onError(err) {
-    if (err.code === 'ENOENT') {
-      stream.respond({ ':status': 404 });
-    } else {
-      stream.respond({ ':status': 500 });
+    // stream.respond() can throw if the stream has been destroyed by
+    // the other side.
+    try {
+      if (err.code === 'ENOENT') {
+        stream.respond({ ':status': 404 });
+      } else {
+        stream.respond({ ':status': 500 });
+      }
+    } catch (err) {
+      // Perform actual error handling.
+      console.log(err);
     }
     stream.end();
   }