Label Suggestion produces NPE

ava.lang.NullPointerException: null
	at java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011) ~[?:1.8.0_352]
	at java.util.concurrent.ConcurrentHashMap$KeySetView.add(ConcurrentHashMap.java:4593) ~[?:1.8.0_352]
	at org.nuxeo.ai.metadata.LabelSuggestion.lambda$distinctByKey$0(LabelSuggestion.java:68) ~[nuxeo-ai-core-2.7.13.jar:?]
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174) ~[?:1.8.0_352]
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1384) ~[?:1.8.0_352]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482) ~[?:1.8.0_352]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472) ~[?:1.8.0_352]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[?:1.8.0_352]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:1.8.0_352]
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:566) ~[?:1.8.0_352]
	at org.nuxeo.ai.metadata.LabelSuggestion.keepUniqueOnly(LabelSuggestion.java:63) ~[nuxeo-ai-core-2.7.13.jar:?]
	at java.util.ArrayList.forEach(ArrayList.java:1259) ~[?:1.8.0_352]
	at java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1082) ~[?:1.8.0_352]
	at org.nuxeo.ai.enrichment.EnrichmentMetadata.toMap(EnrichmentMetadata.java:180) ~[nuxeo-ai-core-2.7.13.jar:?]
	at org.nuxeo.ai.services.DocMetadataServiceImpl.saveEnrichment(DocMetadataServiceImpl.java:115) ~[nuxeo-ai-core-2.7.13.jar:?]
	at org.nuxeo.ai.functions.SaveEnrichmentFunction.lambda$null$0(SaveEnrichmentFunction.java:42) ~[nuxeo-ai-core-2.7.13.jar:?]
	at org.nuxeo.ecm.core.api.CoreInstance$1.run(CoreInstance.java:186) ~[nuxeo-core-api-10.10-HF68.jar:?]
	at org.nuxeo.ecm.core.api.UnrestrictedSessionRunner.runUnrestricted(UnrestrictedSessionRunner.java:137) ~[nuxeo-core-api-10.10-HF68.jar:?]
	at org.nuxeo.ecm.core.api.CoreInstance.doPrivileged(CoreInstance.java:188) ~[nuxeo-core-api-10.10-HF68.jar:?]
	at org.nuxeo.ai.functions.SaveEnrichmentFunction.lambda$accept$1(SaveEnrichmentFunction.java:40) ~[nuxeo-ai-core-2.7.13.jar:?]
	at org.nuxeo.runtime.transaction.TransactionHelper.runInTransaction(TransactionHelper.java:667) ~[nuxeo-runtime-jtajca-10.10-HF63.jar:?]
	at org.nuxeo.runtime.transaction.TransactionHelper.runInTransaction(TransactionHelper.java:646) ~[nuxeo-runtime-jtajca-10.10-HF63.jar:?]
	at org.nuxeo.ai.functions.SaveEnrichmentFunction.accept(SaveEnrichmentFunction.java:40) ~[nuxeo-ai-core-2.7.13.jar:?]