fix: _str_ handling for empty show

src/aura_engine/scheduling/domain.py

@@ -376,7 +376,10 @@ class Timeslot:
         """
         start = SimpleUtil.fmt_time(self.start)
         end = SimpleUtil.fmt_time(self.end)
-        return f"ID#{self.id}: {start} - {end} [Show#{self.show.id}: {self.show.name}]"
+        s = f"ID#{self.id}: {start} - {end}"
+        if self.show:
+            s += f" [Show#{self.show.id}: {self.show.name}]"
+        return s
 
 
 class PlaylistType(enum.Enum):