TypeError: String.isString is not a function

[guiconti]

View details in Rollbar: https://rollbar.com/guiconti/reporter/items/3/

TypeError: String.isString is not a function
  File "/Users/guiconti/GitHub/reporter/server/utils/validator.js", line 15, in Object.exports.isValidString.stringToValidate [as isValidString]
      return String.isString(stringToValidate) && stringToValidate.trim().length > 0;
  File "/Users/guiconti/GitHub/reporter/server/controllers/sendError.js", line 31, in module.exports
      if (!validator.isValidString(data.item.title))
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/layer.js", line 95, in Layer.handle [as handle_request]
        fn(req, res, next);
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/route.js", line 137, in next
          layer.handle_request(req, res, next);
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/route.js", line 112, in Route.dispatch
      next();
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/layer.js", line 95, in Layer.handle [as handle_request]
        fn(req, res, next);
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/index.js", line 281, in <unknown>
            return layer.handle_request(req, res, next);
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/index.js", line 354, in param
          return done();
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/index.js", line 365, in param
          return param();
  File "/Users/guiconti/GitHub/reporter/node_modules/express/lib/router/index.js", line 410, in Function.process_params
      param();