in an exporter script, card.styling has invalid data

[djackddonovan]

In an exporter script, card.styling is not correctly set by reflection when the card uses the default set stylesheet, with has_styling (Options specific to this card).

This is due to an issue in src\data\card.cpp:
When running an exporter script, in IMPLEMENT_REFLECTION(Card), stylesheet_for_reading() is always null for some reason, so REFLECT(styling_data) is skipped.