fix(proxy): handle error when proxy itself errors (#13929)

Author: chaejunlee

packages/vite/src/node/server/middlewares/proxy.ts

@@ -52,8 +52,17 @@ export function proxyMiddleware(
 
     proxy.on('error', (err, req, originalRes) => {
       // When it is ws proxy, res is net.Socket
-      const res = originalRes as http.ServerResponse | net.Socket
-      if ('req' in res) {
+      // originalRes can be falsy if the proxy itself errored
+      const res = originalRes as http.ServerResponse | net.Socket | undefined
+      if (!res) {
+        config.logger.error(
+          `${colors.red(`http proxy error: ${err.message}`)}\n${err.stack}`,
+          {
+            timestamp: true,
+            error: err,
+          },
+        )
+      } else if ('req' in res) {
         config.logger.error(
           `${colors.red(`http proxy error at ${originalRes.req.url}:`)}\n${
             err.stack