Hi Alan,

After updating to bootstrap 4.3.1 sorting arrow icons in the table headers disappeared. Is there a specific version of bootstrap 4 i need to use or am I missing something?
I'm using react-bootstrap-table 1.1.3
Thank you in advance.

```
const columns = [{
dataField: 'id',
text: 'ID',
sort: true
}, {
dataField: 'applicationName',
text: 'Application',
sort: true
}, {
dataField: 'collectionName',
text: 'Collection',
sort: true
}, {
dataField: 'licenseType',
text: 'License',
sort: true
}, {
dataField: 'cost',
text: 'Cost',
sort: true
}, {
dataField: 'approvers',
text: 'Approvers',
sort: true

}];
const defaultSorted = [{
dataField: 'applicationName',
order: 'desc'
}];

class TestTable extends Component {
render() {
return (

);
}
}
export default TestTable;
```

Start by reproducing the reported example with react-bootstrap-table 1.1.3, Bootstrap 4.3.1, the bootstrap4 prop, and sortable columns. Inspect the BootstrapTable rendering and styling entry points to determine whether the arrows are omitted or hidden; done means identifying the compatibility cause and restoring or documenting the expected sorting icons.

Written by the indexing model from the issue text.