Provide feedback on dashboard when shared filter is deleted or unshared

If one create a portlet from a shared filter and then the filter is being unshared or deleted, on the user's dashboard an empty portlet with the header saying:

Issues: ???
This portlet is not valid as the associated filter or field could not be retrieved. (Edit Portlet | Delete Portlet)

is going to be displayed.

As per below example:

and after the filter is 'unshared'

Lack of feedback in the dashboard re reason why the portlet is not displayed correctly can be confusing for users (resulting in SAC cases). This problem might become apparent for users who used the filter for some time and are unaware of the change to the underling filter.

We could possibly display a message in the portlet saying 'Shared filter removed by xxxx'.