Handle selection reset

Author: oowekyala

src/main/java/net/sourceforge/pmd/util/fxdesigner/util/DesignerUtil.java

@@ -307,7 +307,8 @@ public static Optional<String> stackTraceToXPath(Throwable e) {
 
 
     public static RelatedNodesSelector getDefaultRelatedNodesSelector() {
-        return node -> node instanceof ScopedNode ? getNameOccurrences((ScopedNode) node) : Collections.emptyList();
+        return node -> node instanceof ScopedNode ? getNameOccurrences((ScopedNode) node)
+                                                  : Collections.emptyList();
     }
 
     private static List<Node> getNameOccurrences(ScopedNode node) {

src/main/java/net/sourceforge/pmd/util/fxdesigner/util/controls/NodeEditionCodeArea.java

@@ -315,13 +315,11 @@ public void setFocusNode(final Node node, DataHolder options) {
         // editor is only restyled if the selection has changed
         Platform.runLater(() -> styleNodes(node == null ? emptyList() : singleton(node), StyleLayerIds.FOCUS, true));
 
-        Platform.runLater(() -> relatedNodesSelector.ifPresent(selector -> {
-            List<Node> nodes = selector.getHighlightedNodesWhenSelecting(node);
-            highlightRelatedNodes(Objects.requireNonNull(nodes,
-                                                         "RelatedNodesSelection for language "
-                                                             + globalLanguageProperty().getValue().getName()
-                                                             + " returned null"));
-        }));
+        if (node == null) {
+            highlightRelatedNodes(emptyList());
+        } else {
+            Platform.runLater(() -> highlightRelatedNodes(relatedNodesSelector.getValue().getHighlightedNodesWhenSelecting(node)));
+        }
     }