Random errors and NullPointerExceptions in ChainIndex

[novoj]

On of the mentioned problems found in error log:

2024-04-23T13:23:04.095517031Z Caused by: java.lang.NullPointerException: Cannot invoke "io.evitadb.index.array.TransactionalUnorderedIntArray.getLastRecordId()" because "predecessorChain" is null
2024-04-23T13:23:04.095520610Z 	at io.evitadb.index.attribute.ChainIndex.mergeSuccessorChainToElementChainIfPossible(ChainIndex.java:757)
2024-04-23T13:23:04.095523590Z 	at io.evitadb.index.attribute.ChainIndex.attemptToCollapseChain(ChainIndex.java:732)
2024-04-23T13:23:04.095526790Z 	at io.evitadb.index.attribute.ChainIndex.collapseChainsIfPossible(ChainIndex.java:716)
2024-04-23T13:23:04.095529990Z 	at java.base/java.util.OptionalInt.ifPresent(OptionalInt.java:165)
2024-04-23T13:23:04.095533120Z 	at io.evitadb.index.attribute.ChainIndex.removePredecessorFromChain(ChainIndex.java:348)
2024-04-23T13:23:04.095536120Z 	at io.evitadb.index.attribute.ChainIndex.removePredecessor(ChainIndex.java:241)
2024-04-23T13:23:04.095538850Z 	at io.evitadb.index.attribute.AttributeIndex.removeSortAttribute(AttributeIndex.java:374)
2024-04-23T13:23:04.095546300Z 	at io.evitadb.index.EntityIndex.removeSortAttribute(EntityIndex.java:103)
2024-04-23T13:23:04.095549370Z 	at io.evitadb.index.mutation.AttributeIndexMutator.lambda$executeAttributeUpsert$9(AttributeIndexMutator.java:153)
2024-04-23T13:23:04.095552320Z 	at java.base/java.util.Optional.ifPresent(Optional.java:178)
2024-04-23T13:23:04.095555610Z 	at io.evitadb.index.mutation.AttributeIndexMutator.executeAttributeUpsert(AttributeIndexMutator.java:152)
2024-04-23T13:23:04.095558640Z 	at io.evitadb.index.mutation.EntityIndexLocalMutationExecutor.updateAttributes(EntityIndexLocalMutationExecutor.java:390)
2024-04-23T13:23:04.095561480Z 	at io.evitadb.index.mutation.ReferenceIndexMutator.attributeUpdate(ReferenceIndexMutator.java:159)
2024-04-23T13:23:04.095564430Z 	at io.evitadb.index.mutation.EntityIndexLocalMutationExecutor.updateReferences(EntityIndexLocalMutationExecutor.java:486)
2024-04-23T13:23:04.095567440Z 	at io.evitadb.index.mutation.EntityIndexLocalMutationExecutor.applyMutation(EntityIndexLocalMutationExecutor.java:235)
2024-04-23T13:23:04.095570440Z 	at io.evitadb.core.EntityCollection.processMutations(EntityCollection.java:272)
2024-04-23T13:23:04.095573520Z 	at io.evitadb.core.EntityCollection.lambda$applyMutations$41(EntityCollection.java:1506)
2024-04-23T13:23:04.095576420Z 	at io.evitadb.store.entity.serializer.EntitySchemaContext.executeWithSchemaContext(EntitySchemaContext.java:90)
2024-04-23T13:23:04.095579370Z 	at io.evitadb.core.EntityCollection.applyMutations(EntityCollection.java:1504)
2024-04-23T13:23:04.095582180Z 	at io.evitadb.core.EntityCollection.upsertEntityInternal(EntityCollection.java:1396)
2024-04-23T13:23:04.095585040Z 	at io.evitadb.core.EntityCollection.upsertEntity(EntityCollection.java:546)
2024-04-23T13:23:04.095588020Z 	at io.evitadb.core.EvitaSession.lambda$upsertEntity$37(EvitaSession.java:874)
2024-04-23T13:23:04.095590910Z 	at io.evitadb.core.EvitaSession.lambda$executeInTransactionIfPossible$58(EvitaSession.java:1386)
2024-04-23T13:23:04.095594040Z 	at io.evitadb.core.Transaction.executeInTransactionIfProvided(Transaction.java:149)
2024-04-23T13:23:04.095597000Z 	at io.evitadb.core.EvitaSession.executeInTransactionIfPossible(EvitaSession.java:1384)
2024-04-23T13:23:04.095599930Z 	at io.evitadb.core.EvitaSession.upsertEntity(EvitaSession.java:872)
2024-04-23T13:23:04.095602750Z 	at jdk.internal.reflect.GeneratedMethodAccessor61.invoke(Unknown Source)
2024-04-23T13:23:04.095609300Z 	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
2024-04-23T13:23:04.095612350Z 	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
2024-04-23T13:23:04.095615360Z 	at io.evitadb.core.SessionRegistry$EvitaSessionProxy.lambda$invoke$0(SessionRegistry.java:195)
2024-04-23T13:23:04.095618670Z 	... 26 more

We need to write better fuzzy tests that would allow us to exterminate the edge cases in the ChainIndex. It seems that the real production systems may behave sometimes chaotically till they return back to consistent state.