During development of my conference demo, I faced a series of UI issues, most of them related to using null as defaultItemId in the ContentConnector.

Most of the fixes actually go in two directions:

• preventing NPEs with null checks
• null must never be added to the list of selected items

Here's the complete list:

• NPE in WorkbenchPresenter if contentConnector's defaultItemId is null
• NPE in AbstractContentPresenterBase if contentConnector's defaultItemId is null
• No visible section in action bar if defaultItemId is null
• Dialog actions are not available if dialog operates on a simple item (i.e. not a JCR adapter)
  • FormDialogPresenterImpl#filterActions should be restrictive, not additive
• NPE when checking availability if no action matches defined name in action bar (BrowserSubApp)