Wrong start and end dates in iCal file when using a single date field

I have a content type with a single-value field_date and this is what I get in the iCal file:

DTSTART:00000101T000000Z
DTEND:00000101T000000Z

If I switch field_date to multiple, the correct DTSTART and DTEND dates are written to the file.

I traced this back to calendar_plugin_row_ical_node.inc where $delta_field on line 77 is '0' with single value fields. Using isset() instead of !empty() on line 78 fixed it for me, but I don't have an understanding of how this module is constructed so it might be a completely wrong idea.