fix(handlers.js): server crash when target ws server closes.

Author: chimurai

index.js

@@ -110,8 +110,10 @@ var httpProxyMiddleware = function (context, opts) {
     }
 
     function proxyErrorLogger (err, req, res) {
+        var hostname = (req.hostname || req.host) || (req.headers && req.headers.host) // (node0.10 || node 4/5) || (websocket)
         var targetUri = proxyOptions.target.host + req.url;
-        logger.error('[HPM] Proxy error: %s. %s -> "%s"', err.code, req.hostname, targetUri);
+
+        logger.error('[HPM] Proxy error: %s. %s -> "%s"', err.code, hostname, targetUri);
     }
 
 };

lib/handlers.js

@@ -4,8 +4,10 @@ module.exports = {
 
 function proxyError (err, req, res) {
     var host = (req.headers && req.headers.host);
-    if (!res.headersSent) {
+
+    if (res.writeHead && !res.headersSent) {
         res.writeHead(500);
     }
+
     res.end('Error occured while trying to proxy to: '+ host + req.url);
 };