TestFSTs.testRandomWords reproducible NPE

### Description

`./gradlew :lucene:core:test --tests "org.apache.lucene.util.fst.TestFSTs.testRandomWords" -Ptests.seed=5E5E16BC74CD0647`

```
org.apache.lucene.util.fst.TestFSTs > testRandomWords FAILED
java.lang.NullPointerException: Cannot invoke "org.apache.lucene.util.fst.FST.getMetadata()" because "fst" is null
at __randomizedtesting.SeedInfo.seed([5E5E16BC74CD0647:20CFAD83BDC2A982]:0)
at org.apache.lucene.tests.util.fst.FSTTester.doTest(FSTTester.java:291)
at org.apache.lucene.util.fst.TestFSTs.doTest(TestFSTs.java:217)
at org.apache.lucene.util.fst.TestFSTs.testRandomWords(TestFSTs.java:306)
at org.apache.lucene.util.fst.TestFSTs.testRandomWords(TestFSTs.java:281)
```

### Version and environment details

_No response_

Run ./gradlew :lucene:core:test --tests "org.apache.lucene.util.fst.TestFSTs.testRandomWords" -Ptests.seed=5E5E16BC74CD0647 to reproduce the failure. Read TestFSTs.java around testRandomWords and doTest, then inspect FSTTester.java around line 291 to determine why fst is null and what the surrounding tests expect when this case completes.

Written by the indexing model from the issue text.