Issue in Angular UI Calendar

Hello,
I have an issue in ui calendar, when i am adding “div ui-calendar ng-model=“eventSources”>” in Html console shows error
TypeError: Cannot read property ‘length’ of undefined
at allEvents (lib.js:29)
at Object.changeWatcher.getTokens (lib.js:29)
at Scope.$get.Scope.$digest (lib.js:8)
at Scope.$get.Scope.$apply (lib.js:8)
at done (lib.js:7)
at completeRequest (lib.js:7)
at XMLHttpRequest.xhr.onload (lib.js:7)

and lib.js:29 here calender.js is present, it shows
can you plz help me.