When inserting links to other Org items or to the currently clocked-in item, the
complete target headline is used as a description in the newly inserted link.
When that target headline is itself a link, the newly inserted link will contain
the complete link as a description, rendering it unreadable and also
malformed (it's not allowed to have two consequtive brackets in the description
of a link). To remedy this, we now explicitly check the target headline for
being a link, and if so, only use the description of it as the description in
the newly inserted link.