bucket aggregations: render only if several buckets

* closes zenodo/rdm-project#218

Author: anikachurilova

src/lib/components/BucketAggregation/BucketAggregation.js

@@ -67,7 +67,7 @@ class BucketAggregation extends Component {
       this.props;
     const selectedFilters = this._getSelectedFilters(userSelectionFilters);
     const resultBuckets = this._getResultBuckets(resultsAggregations);
-    const valuesCmp = resultBuckets.length
+    const valuesCmp = resultBuckets.length > 1
       ? this._renderValues(resultBuckets, selectedFilters)
       : null;
     return (