Trying to implement angularJs $uibModal but is it not popping up. Giving an error angular.min.js:129 Possibly unhandled rejection: backdrop click

Trying to implement angularJs $uibModal but is it not popping up. Giving an error angular.min.js:129 Possibly unhandled rejection: backdrop click

(function(){ angular .module('ubwinoApp') .controller('scheduleCtrl', scheduleCtrl);

   scheduleCtrl.$inject = ['$location','$uibModal','authentication'];

   function scheduleCtrl($location, $uibModal, authentication){
    
    var vm = this;
    vm.currentPath = $location.path();
    vm.isLoggedIn = authentication.isLoggedIn();
    vm.currentUser = authentication.currentUser();

    vm.popupEventForm = function(){
        var modalInstance = $uibModal.open({
              templateUrl: '/eventModal/eventModal.view.html',
              controller: 'eventModalCtrl as vm',
              backdrop: false,
            });
      // alert("Lets add an event"); 
    }
   
   }

})()

(function () {

angular
.module('ubwinoApp')
.controller('eventModalCtrl', eventModalCtrl);

  eventModalCtrl.$inject = ['$uibModalInstance'];
  function eventModalCtrl($uibModalInstance){
      var vm = this;
      vm.modal = {
        close : function(result){
          $uibModalInstance.close(result);
        },
        cancel : function () {
            $uibModalInstance.dismiss('cancel');
        }
    };
}

})();