Prevent console errors on first listview load

One minor "bug" (in quote marks because it's not causing any
user-visible problems, just a lot of extraneous Javascript console
messages) in the listview directive is that, since Angular fires
watches once before the page loads, the value of $scope.items was
undefined the first time the watches fired -- which led to setting
$scope.filteredItems = $scope.items and then trying to take values
like $scope.filteredItems.length (which, when $scope.filteredItems
is undefined, becomes undefined.length and prints a console error).
To prevent the problem, we set $scope.items to an empty list in the
controller, so that the watch fires on an empty list rather than on
an undefined value.