code: void handleFileTreeValueChange() {
  
          Item resourceItem = m_treeContainer.getItem(m_fileTree.getValue());
          if (resourceItem != null) {
              if ((resourceItem.getItemProperty(CmsResourceTableProperty.PROPERTY_DISABLED).getValue() != null)
                  && ((Boolean)resourceItem.getItemProperty(
                      CmsResourceTableProperty.PROPERTY_DISABLED).getValue()).booleanValue()) {
                  // in case the folder is disabled due to missing visibility, reset the value to the previous one
                  m_fileTree.setValue(m_selectTreeFolder);
  
              } else {
                  m_selectTreeFolder = (CmsUUID)m_fileTree.getValue();
              }
          }
      }
docs: Handles the file tree value changes.<p>