Receiving Type Error Cannot Read 'length' ionic.bundle.js

I am receiving Uncaught TypeError: Cannot read property 'length' of undefined error on the load of a certain page of my ionic app.

Because this error points to a file in the core, I am clueless as to how to debug this. I have performed breakpoints throughout the controller file and I am unable to pin it down.

The error comes up after the full page has loaded.

Hopefully this picture paints a 1000 words.

EDIT

I have now tracked this issue to this piece of code.

$ionicModal.fromTemplateUrl('templates/exercise-modal.html', {
  scope: $scope
}).then(function (addExerciseModal) {
  $scope.addExerciseModal = addExerciseModal;
});

// Triggered in the exercise modal to close it
$scope.closeAddExerciseModal = function() {
  $scope.addExerciseModal.hide();
};

// Open the exercise modal
$scope.OpenAddExerciseModal = function() {
    $ionicSlideBoxDelegate.slide(0);
    $scope.addExerciseModal.show();
};

However I use this elsewhere in my app and it functions just fine..?