ics: make speaker name appear if title is "TBA"

naomod_weekly_seminars.ics

@@ -34,7 +34,7 @@ BEGIN:VEVENT
 UID:{{ post.date | date: "%Y%m%d" }}@naomod.github.io
 ORGANIZER;CN=Erwan BOUSSE:mailto:[email protected]
 LOCATION: See room reservation calendar.
-SUMMARY:{{ post.title }}
+SUMMARY:{% if post.title == "TBA" %}Talk by {{ post.speaker }}{% else %}{{ post.title }}{% endif %}
 DESCRIPTION:Speaker: {{ post.speaker }}.\n\n{{ post.content | normalize_whitespace | strip }}
 CLASS:PUBLIC
 DTSTART;TZID=Europe/Paris:{{ post.date | date: "%Y%m%d" }}T{{post.start}}00