fixed crash by calling loadAsync on GeodatabaseFeatureTable

Author: tschie

src/main/java/com/esri/samples/featurelayers/feature_layer_geodatabase/FeatureLayerGeodatabase.java

@@ -61,7 +61,7 @@ public void start(Stage stage) throws Exception {
       geodatabase.addDoneLoadingListener(() -> {
         // access the geodatabase's feature table Trailheads
         GeodatabaseFeatureTable geodatabaseFeatureTable = geodatabase.getGeodatabaseFeatureTable("Trailheads");
-
+        geodatabaseFeatureTable.loadAsync();
         // create a layer from the geodatabase feature table above and add to map
         FeatureLayer featureLayer = new FeatureLayer(geodatabaseFeatureTable);
         featureLayer.addDoneLoadingListener(() -> {