Catch error due to invalid status code (#95)

lib/cors-anywhere.js

@@ -101,7 +101,18 @@ function proxyRequest(req, res, proxy) {
           }
           return proxyReqOn.call(this, 'response', function(proxyRes) {
             if (onProxyResponse(proxy, proxyReq, proxyRes, req, res)) {
-              listener(proxyRes);
+              try {
+                listener(proxyRes);
+              } catch (err) {
+                // Wrap in try-catch because an error could occur:
+                // "RangeError: Invalid status code: 0"
+                // https://github.com/Rob--W/cors-anywhere/issues/95
+                // https://github.com/nodejitsu/node-http-proxy/issues/1080
+
+                // Forward error (will ultimately emit the 'error' event on our proxy object):
+                // https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-incoming.js#L134
+                proxyReq.emit('error', err);
+              }
             }
           });
         };
@@ -400,6 +411,14 @@ exports.createServer = function createServer(options) {
       // the headers because it would generate an error.
       return;
     }
+
+    // When the error occurs after setting headers but before writing the response,
+    // then any previously set headers must be removed.
+    var headerNames = res.getHeaderNames ? res.getHeaderNames() : Object.keys(res._headers);
+    headerNames.forEach(function(name) {
+      res.removeHeader(name);
+    });
+
     res.writeHead(404, {'Access-Control-Allow-Origin': '*'});
     res.end('Not found because of proxy error: ' + err);
   });