This type error is raised:

TypeError: $scope.submitFunction(...) is not a function
at ChatCtrl.submitFunction (index.js:128)
at angular.js:12474
at f (angular.js:21700)
at n.$eval (angular.js:14570)
at n.$apply (angular.js:14669)
at HTMLFormElement. (angular.js:21705)
at HTMLFormElement.c (angular.js:3047)

Any idea why this happens? Is there an updated version I should download?