Leave empty space below charts for the author card

The author card was cut for the last authors at the bottom of a
chart on the bottom edge of the page.
Add missing declaration of local variable limit
Handle categories not selected in getAuthorsSelectedInGroup()

An empty list is now correctly returned in this case, which
used to result in a failure. This issue was introduced when
converting the previous algorithm, which computed the number
of authors without keeping the list, missing the fact that
a total of zero authors was returned by default when the
category was not found.
Replace 'working in' with 'working for' in menu sentence
Add chapters in contribution codes, remove multiplier

The chapter is now displayed in author card,
which completes the card.