Issues with Lucene and ticket branches

[flaix]

Observed various errors in the log after trying out the --add-opens for Java 17. This is unrelated, but what I did was:
Unpack the Gb tarball
Run it
Copy over the test git repos from my working copy
Run reindex-tickets
It complained about no ticket service being set
Set the BranchTicketService
Ran reindex-tickets again. No problem.
Then a few restarts of Gb under Java 17 and Java 11.

Now under Java 11 the following was observed.

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.lucene.store.MMapDirectory$1 (file:/Users/florian/Devel/Github/Gitblitd/gitblit-1.9.2-SNAPSHOT/ext/lucene-core-5.5.2.jar) to method java.nio.DirectByteBuffer.cleaner()
WARNING: Please consider reporting this to the maintainers of org.apache.lucene.store.MMapDirectory$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
2021-12-09 22:19:59 [ERROR] Exception while updating tickets/branch.git Lucene index
java.lang.NullPointerException
	at com.gitblit.service.LuceneService.updateIndex(LuceneService.java:772)
	at com.gitblit.service.LuceneService.index(LuceneService.java:213)
	at com.gitblit.service.LuceneService.run(LuceneService.java:179)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:834)
2021-12-09 22:19:59 [ERROR] Could not update tickets/branch.git Lucene index!

After running reindex-tickets again, running Gb under Java 17:

2021-12-09 22:22:24 [ERROR] Exception while updating tickets/branch.git Lucene index
java.lang.NullPointerException: Cannot invoke "com.gitblit.models.RefModel.getName()" because "branch" is null
	at com.gitblit.service.LuceneService.updateIndex(LuceneService.java:772)
	at com.gitblit.service.LuceneService.index(LuceneService.java:213)
	at com.gitblit.service.LuceneService.run(LuceneService.java:179)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
	at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:833)
2021-12-09 22:22:24 [ERROR] Could not update tickets/branch.git Lucene index!