fix: correct mode check in ssrRender function

src/server-node.tsx

@@ -30,7 +30,7 @@ async function ssrRender(res: http.ServerResponse, mode: 'server' | 'client' = '
     res.end('dist/index.html not found');
     return;
   }
-  if (!mode) {
+  if (mode === 'client'   ) {
     res.writeHead(200, { 'Content-Type': 'text/html' });
     res.end(template);
     return;