NullPointerException in QueryComponent

In our production deployment of Solr, running 8.6, we see the following stacktrace (truncated):

java.lang.NullPointerException at org.apache.solr.handler.component.QueryComponent.mergeIds(QueryComponent.java:873) at org.apache.solr.handler.component.QueryComponent.handleRegularResponses(QueryComponent.java:628) at org.apache.solr.handler.component.QueryComponent.handleResponses(QueryComponent.java:607)