Notifications cannot be set on posts without comments or likes

I'm using talkyard as the commenting system on my blog: https://outde.xyz. Some of my blog's readers would like to get notifications for specific posts even if there are no comments yet. This does not work for two reasons:

1. Without any comments, the vertical height of the pull-down menu for notifications is too small. The menu gets clipped vertically. As a result, the Every post option is barely visible (only a blue line at the very top).

2. Since the comment thread hasn't been created yet, selecting any notification option produces an Internal Server Error (copy-pasted at the end). I currently work around that by liking every new post, but that's tedious.

You can test this yourself for this old post (I hope nobody comments or likes it in the meantime): https://outde.xyz/2019-04-20/adding-metadata-to-your-article.html#adding-metadata-to-your-article

Error 500 Internal Server Error
Something went wrong: [DwE500EXC]

org.postgresql.util.PSQLException: ERROR: insert or update on table "page_notf_prefs3" violates foreign key constraint "pagenotfprefs_r_pages"
  Detail: Key (site_id, page_id)=(440, 0) is not present in table "pages3".
	at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2440)
	at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2183)
	at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:308)
	at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
	at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
	at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:150)
	at org.postgresql.jdbc.PgPreparedStatement.executeUpdate(PgPreparedStatement.java:127)
	at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeUpdate(ProxyPreparedStatement.java:61)
	at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeUpdate(HikariProxyPreparedStatement.java)
	at com.debiki.dao.rdb.Rdb.execImpl(Rdb.scala:492)
	at com.debiki.dao.rdb.Rdb.update(Rdb.scala:454)
	at com.debiki.dao.rdb.RdbSiteTransaction.runUpdate(RdbSiteTransaction.scala:282)
	at com.debiki.dao.rdb.RdbSiteTransaction.runUpdateSingleRow(RdbSiteTransaction.scala:287)
	at com.debiki.dao.rdb.PageNotfPrefsSiteTxMixin.upsertPageNotfPref(PageNotfPrefsSiteTxMixin.scala:85)
	at com.debiki.dao.rdb.PageNotfPrefsSiteTxMixin.upsertPageNotfPref$(PageNotfPrefsSiteTxMixin.scala:47)
	at com.debiki.dao.rdb.RdbSiteTransaction.upsertPageNotfPref(RdbSiteTransaction.scala:38)
	at debiki.dao.UserDao.$anonfun$savePageNotfPref$1(UserDao.scala:1267)
	at debiki.dao.UserDao.$anonfun$savePageNotfPref$1$adapted(UserDao.scala:1266)
	at debiki.dao.UserDao.$anonfun$editMemberThrowUnlessSelfStaff$1(UserDao.scala:1637)
	at debiki.dao.UserDao.$anonfun$editMemberThrowUnlessSelfStaff2$4(UserDao.scala:1671)
	at debiki.dao.SiteDao.$anonfun$readWriteTransaction$2(SiteDao.scala:155)
	at com.debiki.core.DbDao2.readWriteSiteTransaction(DbDao2.scala:67)
	at debiki.dao.SiteDao.$anonfun$readWriteTransaction$1(SiteDao.scala:155)
	at debiki.dao.SiteDao$.synchronizeOnSiteId(SiteDao.scala:450)
	at debiki.dao.SiteDao.readWriteTransaction(SiteDao.scala:154)
	at debiki.dao.UserDao.editMemberThrowUnlessSelfStaff2(UserDao.scala:1660)
	at debiki.dao.UserDao.editMemberThrowUnlessSelfStaff2$(UserDao.scala:1648)
	at debiki.dao.SiteDao.editMemberThrowUnlessSelfStaff2(SiteDao.scala:71)
	at debiki.dao.UserDao.editMemberThrowUnlessSelfStaff(UserDao.scala:1636)
	at debiki.dao.UserDao.editMemberThrowUnlessSelfStaff$(UserDao.scala:1634)
	at debiki.dao.SiteDao.editMemberThrowUnlessSelfStaff(SiteDao.scala:71)
	at debiki.dao.UserDao.savePageNotfPref(UserDao.scala:1266)
	at debiki.dao.UserDao.savePageNotfPref$(UserDao.scala:1265)
	at debiki.dao.SiteDao.savePageNotfPref(SiteDao.scala:71)
	at controllers.UserController.$anonfun$saveContentNotfPref$1(UserController.scala:1135)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:57)
	at ed.server.http.PlainApiActions$$anon$1.runBlockIfAuthOk(PlainApiActions.scala:406)
	at ed.server.http.PlainApiActions$$anon$1.invokeBlockAuthViaCookie(PlainApiActions.scala:231)
	at ed.server.http.PlainApiActions$$anon$1.invokeBlock(PlainApiActions.scala:123)
	at ed.server.http.PlainApiActions$$anon$1.invokeBlock(PlainApiActions.scala:83)
	at play.api.mvc.ActionBuilder$$anon$2.apply(Action.scala:419)
	at ed.server.http.PlainApiActions$$anon$1.$anonfun$composeAction$1(PlainApiActions.scala:97)
	at ed.server.http.SafeActions$ExceptionAction$.invokeBlock(SafeActions.scala:115)
	at ed.server.http.SafeActions$ExceptionAction$.invokeBlock(SafeActions.scala:82)
	at play.api.mvc.ActionBuilder$$anon$2.apply(Action.scala:419)
	at play.api.mvc.Action.$anonfun$apply$2(Action.scala:96)
	at play.api.libs.streams.StrictAccumulator.$anonfun$mapFuture$4(Accumulator.scala:174)
	at scala.util.Try$.apply(Try.scala:213)
	at play.api.libs.streams.StrictAccumulator.$anonfun$mapFuture$3(Accumulator.scala:174)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:57)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:57)
	at play.api.libs.streams.StrictAccumulator.run(Accumulator.scala:211)
	at play.core.server.AkkaHttpServer.$anonfun$runAction$4(AkkaHttpServer.scala:377)
	at akka.http.scaladsl.util.FastFuture$.strictTransform$1(FastFuture.scala:41)
	at akka.http.scaladsl.util.FastFuture$.$anonfun$transformWith$3(FastFuture.scala:51)
	at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
	at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:55)
	at akka.dispatch.BatchingExecutor$BlockableBatch.$anonfun$run$1(BatchingExecutor.scala:91)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
	at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:85)
	at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:91)
	at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40)
	at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(ForkJoinExecutorConfigurator.scala:44)
	at akka.dispatch.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
	at akka.dispatch.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
	at akka.dispatch.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
	at akka.dispatch.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)