Undefined columns in sortInfo

When using server side sorting, the init() method attempts to set sortInfo.columns before $scope.columns is defined (before the buildColumns method has executed). It throws an error, and the grid is not displayed on the page.

See this plunker to show my point: http://plnkr.co/edit/7pbZp4. I have attached a custom ng-grid.debug.js, and compared it to the one in the main repo. Also, please note that the sorting won't work because in the plunker I used a static json file.