NoSuchElementException with behavior enabled and package not installed

The behavior is registered via ZCML so it is available even if the package is not installed; this could lead to a confusion like in my case: I spent a couple of hours trying to figure out why I was getting a webdriver `NoSuchElementException` when creating an item with the behavior enabled: the `featuredimage` view used to generate the image is not available as it is registered only if the browser layer is available.

We need to find out a workaround for this or to skip the subscriber if the package is not installed.

Start by tracing the ZCML behavior registration, the featuredimage view, the browser-layer condition, and the subscriber described in the issue. Reproduce item creation with the behavior enabled while the package is unavailable, then determine whether the subscriber can be skipped safely or a workaround is needed. Done means item creation no longer raises NoSuchElementException in that situation.

Written by the indexing model from the issue text.