Allow empty yahrzeit ics download (e.g. with no VEVENTs)

package.json

@@ -49,7 +49,7 @@
     "@hebcal/core": "^5.4.5",
     "@hebcal/geo-sqlite": "^5.0.5",
     "@hebcal/hdate": "^0.10.1",
-    "@hebcal/icalendar": "^5.0.6",
+    "@hebcal/icalendar": "^5.1.0",
     "@hebcal/learning": "^5.0.8",
     "@hebcal/leyning": "^8.1.9",
     "@hebcal/locales": "^5.0.1",

src/yahrzeit.js

@@ -479,19 +479,7 @@ export async function yahrzeitDownload(ctx) {
   ctx.state.trace.set('makeYahrzeitEvents-start', Date.now());
   const events = await makeYahrzeitEvents(maxId, query, reminder);
   ctx.state.trace.set('makeYahrzeitEvents-end', Date.now());
-  if (events.length === 0) {
-    ctx.throw(400, 'No events');
-  }
-  let lastModified = details.lastModified;
-  const now = new Date();
-  if (!lastModified) {
-    // An old /v2/y/ URL won't have a lastModified
-    lastModified = now;
-  }
-  const firstEventDt = events[0].getDate().greg();
-  if (firstEventDt > lastModified && firstEventDt < now) {
-    lastModified = firstEventDt;
-  }
+  const lastModified = makeLastModified(details, events);
   query.lastModified = ctx.lastModified = lastModified; // store in query for eTag
   const startYear = parseInt(query.start, 10) || getDefaultStartYear();
   const extension = rpath.substring(rpath.length - 4);
@@ -528,6 +516,23 @@ export async function yahrzeitDownload(ctx) {
   }
 }
 
+function makeLastModified(details, events) {
+  let lastModified = details.lastModified;
+  const now = new Date();
+  if (!lastModified) {
+    // An old /v2/y/ URL won't have a lastModified
+    lastModified = now;
+  }
+  if (events.length === 0) {
+    return lastModified;
+  }
+  const firstEventDt = events[0].getDate().greg();
+  if (firstEventDt > lastModified && firstEventDt < now) {
+    lastModified = firstEventDt;
+  }
+  return lastModified;
+}
+
 /**
  * @return {number}
  */