yet another PlotGroups fix atempt. Seems to be working properly

numass-main/src/main/java/inr/numass/NumassIO.java

@@ -99,7 +99,7 @@ public class NumassIO extends BasicIOManager {
             }
         }
 
-        if (stage != null && stage.length() != 0) {
+        if (stage != null && stage.getLength() != 0) {
             tokens.addAll(Arrays.asList(stage.asArray()));
         }
 

numass-viewer/src/main/kotlin/inr/numass/viewer/StorageView.kt

@@ -134,6 +134,7 @@ class StorageView(private val context: Context = Global.instance()) : View(title
         center {
             splitpane {
                 treeview<Container> {
+                    isShowRoot = false
                     storageProperty.onChange {
                         if (it != null) {
                             root = TreeItem(Container("root", it))