fix: fall back to TBA when a physical workshop has no host

app/serializers/workshop_calendar.rb

@@ -25,7 +25,7 @@ def calendar
 
   def setup_event
     calendar.event do |e|
-      configure(e, host_name: workshop.host.name)
+      configure(e, host_name: workshop.host&.name || 'TBA')
 
       e.location = address(workshop)
       e.description = I18n.t('workshop.calendar.description', invitation_link: invitation_url)
@@ -55,7 +55,7 @@ def configure(event, host_name:)
   end
 
   def address(workshop)
-    AddressPresenter.new(workshop.host.address).to_s
+    workshop.host&.address ? AddressPresenter.new(workshop.host.address).to_s : 'TBA'
   end
 
   def start_and_end_time(event)

spec/serializers/workshop_calendar_spec.rb

@@ -53,6 +53,39 @@
       end
     end
 
+    context 'with a physical workshop that has no host' do
+      let(:workshop) { Fabricate(:workshop_no_sponsor, virtual: false) }
+
+      it 'falls back to TBA for host name and address' do
+        event = calendar.events.first
+
+        expect(event.summary.to_s).to eq('codebar @ TBA')
+        expect(event.location.to_s).to eq('TBA')
+        expect(event.organizer.to_s).to eq(workshop.chapter.email)
+        expect(event.description).to include(invitation_url)
+      end
+
+      it 'serialises the fallback into the iCalendar output' do
+        expect(described_class.new(workshop, invitation_url).ical).to include('TBA')
+      end
+    end
+
+    context 'with a host whose address record has been removed' do
+      let(:workshop) do
+        Fabricate(:workshop).tap do |w|
+          w.host.address.destroy
+          w.reload
+        end
+      end
+
+      it 'keeps the host name and falls back to TBA for the address' do
+        event = calendar.events.first
+
+        expect(event.summary.to_s).to eq("codebar @ #{workshop.host.name}")
+        expect(event.location.to_s).to eq('TBA')
+      end
+    end
+
     context 'with a virtual workshop' do
       let(:workshop) { Fabricate(:virtual_workshop) }