Return error when client headers are missing (issue #19)

Return an error response when headers are missing instead of waiting indefinitely

ExpressAPI/src/middlewares/ClientVersionCheckerMiddleware.ts

@@ -26,6 +26,8 @@ class ClientVersionCheckerMiddleware {
                 }
 
                 new Session().sendResponse(res, HttpStatusCode.MethodNotAllowed, {}, `Unsupported client.`, DojoStatusCode.CLIENT_NOT_SUPPORTED);
+            } else {
+                new Session().sendResponse(res, HttpStatusCode.MethodNotAllowed, {}, `Missing client headers.`, DojoStatusCode.CLIENT_HEADER_MISSING);
             }
         };
     }