clean up fingerprint response

frontend/src/metabase/reference/selectors.js

@@ -167,3 +167,8 @@ export const getGuide = (state, props) => state.reference.guide;
 export const getDashboards = (state, props) => getDashboardListing(state) && resourceListToMap(getDashboardListing(state));
 
 export const getIsDashboardModalOpen = (state, props) => state.reference.isDashboardModalOpen;
+
+
+export const getFieldFingerprint = (state) =>
+    state.reference.fieldFingerprint && state.reference.fieldFingerprint.fingerprint
+

frontend/src/metabase/xray/containers/FieldXray.jsx

@@ -5,6 +5,8 @@ import { connect } from 'react-redux'
 
 import { fetchFieldFingerPrint } from 'metabase/reference/reference'
 
+import { getFieldFingerprint } from 'metabase/reference/selectors'
+
 import LoadingAndErrorWrapper from 'metabase/components/LoadingAndErrorWrapper'
 
 import SimpleHistogram from 'metabase/xray/SimpleHistogram'
@@ -119,11 +121,11 @@ class FieldXRay extends Component {
 }
 
 const mapStateToProps = state => ({
-    fingerprint: state.reference.fieldFingerprint,
+    fingerprint: getFieldFingerprint(state)
 })
 
 const mapDispatchToProps = {
-    fetchFieldFingerPrint: fetchFieldFingerPrint
+    fetchFieldFingerPrint
 }
 
 export default connect(mapStateToProps, mapDispatchToProps)(FieldXRay)