conditionally destroy

lib/http-proxy/passes/web-incoming.js

@@ -144,7 +144,10 @@ module.exports = {
 
     // Ensure we abort proxy if request is aborted
     res.on('close', function () {
-      proxyReq.destroy();
+      const aborted = !res.writableFinished;
+      if (aborted) {
+        proxyReq.destroy();
+      }
     });
 
     // handle errors in proxy and incoming request, just like for forward proxy