can't click on button using horseman

i want to click on button where selector is .nav-submenu li:first, but it shows error code:

.evaluate(function () {
            console.log('-----------------'+selector)
       $('.nav-submenu li:first').click();
    })

error comes :

{ line: 3,
  message: 'null is not an object (evaluating \'$(\'.nav-submenu li:first\').click\')',
  stack: 'fn\n    at Horseman.<anonymous> (/usr/lib/node_modules/node-horseman/lib/actions.js:839:38)\n    at Horseman.tryCatcher (/usr/lib/node_modules/node-horseman/node_modules/bluebird/js/release/util.js:16:23)\n    at Promise._settlePromiseFromHandler (/usr/lib/node_modules/node-horseman/node_modules/bluebird/js/release/promise.js:510:31)\n    at Promise._settlePromise (/usr/lib/node_modules/node-horseman/node_modules/bluebird/js/release/promise.js:567:18)\n    at Promise._settlePromiseCtx (/usr/lib/node_modules/node-horseman/node_modules/bluebird/js/release/promise.js:604:10)\n    at Async._drainQueue (/usr/lib/node_modules/node-horseman/node_modules/bluebird/js/release/async.js:143:12)\n    at Async._drainQueues (/usr/lib/node_modules/node-horseman/node_modules/bluebird/js/release/async.js:148:10)\n    at Immediate.Async.drainQueues (/usr/lib/node_modules/node-horseman/node_modules/bluebird/js/release/async.js:17:14)\n    at runCallback (timers.js:637:20)\n    at tryOnImmediate (timers.js:610:5)\n    at processImmediate [as _immediateCallback] (timers.js:582:5)',
  name: 'Error',
  toString: [Function] }

via Shekhar Tyagi