Program: 69303
Project: 69303
Buggy source:
@Override protected void initForm(FormItemContainer formLayout,Controller listener,UserRequest ureq){
  CoursePropertyManager cpm=courseEnv.getCoursePropertyManager();
  Property prop=cpm.findCourseNodeProperty(rootNode,null,null,"String_Node_Str");
  String value=prop == null ? null : prop.getStringValue();
  List<CatalogEntry> catalogEntries=catalogManager.getCatalogCategoriesFor(repositoryEntry);
  if ("String_Node_Str".equals(value) && !catalogEntries.isEmpty()) {
    value="String_Node_Str";
  }
  FormItemContainer fc=FormLayoutContainer.createDefaultFormLayout("String_Node_Str",getTranslator());
  fc.setRootForm(mainForm);
  formLayout.add("String_Node_Str",fc);
  final String[] keys=new String[]{"String_Node_Str","String_Node_Str"};
  final String[] values=new String[]{translate("String_Node_Str"),translate("String_Node_Str")};
  catalogBox=uifactory.addDropdownSingleselect("String_Node_Str","String_Node_Str",fc,keys,values,null);
  catalogBox.addActionListener(FormEvent.ONCHANGE);
  if (!StringHelper.containsNonWhitespace(value)) {
    value="String_Node_Str";
  }
  catalogBox.select(value,true);
  flc.contextPut("String_Node_Str",value);
  boolean activate="String_Node_Str".equals(value);
  addToCatalog=uifactory.addFormLink("String_Node_Str",flc,Link.BUTTON_SMALL);
  addToCatalog.setElementCssClass("String_Node_Str");
  addToCatalog.setVisible(activate);
  for (  CatalogEntry entry : catalogEntries) {
    CategoryLabel label=new CategoryLabel(entry,entry.getParent(),getPath(entry));
    FormLink link=uifactory.addFormLink(label.getCategoryUUID(),"String_Node_Str",null,flc,Link.LINK);
    link.setUserObject(label);
    deleteLinks.add(link);
  }
  flc.contextPut("String_Node_Str",deleteLinks);
}

Fixed version (ground truth):
@Override protected void initForm(FormItemContainer formLayout,Controller listener,UserRequest ureq){
  CoursePropertyManager cpm=courseEnv.getCoursePropertyManager();
  Property prop=cpm.findCourseNodeProperty(rootNode,null,null,"String_Node_Str");
  String value=prop == null ? null : prop.getStringValue();
  List<CatalogEntry> catalogEntries=catalogManager.getCatalogCategoriesFor(repositoryEntry);
  if ("String_Node_Str".equals(value) && !catalogEntries.isEmpty()) {
    value="String_Node_Str";
  }
  FormItemContainer fc=FormLayoutContainer.createDefaultFormLayout("String_Node_Str",getTranslator());
  fc.setRootForm(mainForm);
  formLayout.add("String_Node_Str",fc);
  final String[] values=new String[]{translate("String_Node_Str"),translate("String_Node_Str")};
  catalogBox=uifactory.addDropdownSingleselect("String_Node_Str","String_Node_Str",fc,keys,values,null);
  catalogBox.addActionListener(FormEvent.ONCHANGE);
  if (!StringHelper.containsNonWhitespace(value)) {
    value="String_Node_Str";
  }
  catalogBox.select(value,true);
  flc.contextPut("String_Node_Str",value);
  boolean activate="String_Node_Str".equals(value);
  addToCatalog=uifactory.addFormLink("String_Node_Str",flc,Link.BUTTON_SMALL);
  addToCatalog.setElementCssClass("String_Node_Str");
  addToCatalog.setVisible(activate);
  for (  CatalogEntry entry : catalogEntries) {
    CategoryLabel label=new CategoryLabel(entry,entry.getParent(),getPath(entry));
    FormLink link=uifactory.addFormLink(label.getCategoryUUID(),"String_Node_Str",null,flc,Link.LINK);
    link.setUserObject(label);
    deleteLinks.add(link);
  }
  flc.contextPut("String_Node_Str",deleteLinks);
}