scrollTabIntoView(arg) won't work if arg is zero

[indianazhao]

If the argInt is equal to zero, scrollTabIntoView will not scroll to the tab 0.
So I change the if-check from truthy value check if(argInt) to number check if(argInt>=0).

$scope.scrollTabIntoView = function(arg){
  if(!$scope.tabContainer || $scope.hideButtons)return;

  var argInt = parseInt(arg);
  var tabToScroll;

  // first we find the tab element.
  if(argInt>=0) { // scroll tab index into view
    var allTabs = $scope.tabContainer.querySelectorAll('ul.nav-tabs > li');
    if(allTabs.length > argInt) { // only if its really exist
      tabToScroll = allTabs[argInt];
    }
  } else { // scroll selected tab into view
    var activeTab = $scope.tabContainer.querySelector('li.active');
    if(activeTab) {
      tabToScroll = activeTab;
    }
  }
...