ui: postpone loading 'details' part of selected item in MasterDetailsComponent until it is shown

For project with many facets initialization of facet type node in Project Structure dialog may take a while (IDEA-185499), but actually user won't see these editors until he clicks on 'Facets' item. This fix will postpone creation of facet type editor until FacetStructureConfigurable is shown.

platform/platform-api/src/com/intellij/openapi/ui/MasterDetailsComponent.java

@@ -350,7 +350,12 @@ public abstract class MasterDetailsComponent implements Configurable, DetailsCom
     if (!selected) {
       TreeUtil.selectFirstNode(myTree);
     }
-    updateSelectionFromTree();
+
+    //'updateSelectionFromTree' initializes 'details' components and it may take some time, so if the component isn't showing now
+    //  it's better to postpone calling it until 'addNotify' is called; in complex dialog like Project Structure the component may not be shown at all.
+    if (myWholePanel != null && myWholePanel.isShowing()) {
+      updateSelectionFromTree();
+    }
   }
 
   protected void loadComponentState() {