[Security&Privacy] Skip uninstalled apps
Created by: mardy
This is a workaround for https://github.com/ubports/ubuntu-touch/issues/385: when building the list of app permissions, skip those apps for which a display name cannot be resolved (meaning that they have most likely been deleted).
This is only a workaround: the application records in the trust-store should actually be removed, once an application gets uninstalled.