Merge pull request #512 from DanielDiBe/headers-sent-fix

Fix issue #496: Cannot set headers after they are sent to the client

plugins/c9.vfs.server/vfs.server.js

@@ -138,7 +138,8 @@ function plugin(options, imports, register) {
             req.on("close", function() {
                 done = true;
                 cancel();
-                res.json({}, 0, 500);
+                if(!res.headersSent)
+                    res.json({}, 0, 500);
             });
         }
     ]);