BrowserViewUniversalListener.connectionOpened is fired on the opening of a connection. In my case, the connection being opened comes from a wizard displaying the BrowserWidget rather than the BrowserView. In this use-case, the BrowserConnection used in the wizard is only temporary so not added to the BrowserCorePlugin ConnectionManager.
Consequently, opening a connection in the wizard while the BrowserView is also open, the latter's BrowserViewUniversalListener.connectionOpened() is fired and a NPE results.
A check can be added to assert that the BrowserConnection fetched from the ConnectionManager is not null. Only if not null should the BrowserView viewer be refreshed.