The public function get_section_dates($section, $startdate = false) is
only defined in format_weeks, not in format_base.
As other formats can (and format_topcoll has) declare a different
get_section_dates public method, merely checking that it exists is not
sufficient to guarantee that it can be called with just a section object.
Check that the format either is, or is a subclass of format_weeks.
Didier 'OdyX' Raboud
cd9c54c93c