Dropdown icon is not visible in combo chart and bar chart after custom theme is applied ver Sep 2018

[NS]

While creating a bar and combo chart with alternate dimensions (cyclic group), on x axis drop down icon is not coming. However if click on the dimension(country) in chart, its giving option to select alternate dimension . But requirement is to show dropdown icon as well.

When I am removing below code from the custom JSON file than combo chart starts showing the dropdown select.

customStyles :[{
"cssRef" :"theme.css",
  "classRef": "sense-theme"
}]