Debug Sampler error when Kafka Producer Config is included in test

[EShubnikova]

If both Kafka Producer Config and Debug Sampler(s) are included in a test, all Debug Samplers produce an error. However Kafka Producer is created without issue and Kafka Producer Samplers are successful.
This is the error:

ERROR o.a.j.t.JMeterThread: Error while processing sampler: 'Debug Sampler'.
java.lang.NullPointerException: Cannot invoke "Object.toString()" because the return value of "java.util.Map$Entry.getKey()" is null
at org.apache.jorphan.util.AlphaNumericKeyComparator.lambda$new$0(AlphaNumericKeyComparator.java:36) ~[jorphan.jar:5.6.2]
at org.apache.jorphan.util.AlphaNumericComparator.compare(AlphaNumericComparator.java:51) ~[jorphan.jar:5.6.2]
at org.apache.jorphan.util.AlphaNumericKeyComparator.compare(AlphaNumericKeyComparator.java:41) ~[jorphan.jar:5.6.2]
at org.apache.jorphan.util.AlphaNumericKeyComparator.compare(AlphaNumericKeyComparator.java:29) ~[jorphan.jar:5.6.2]
at java.util.TimSort.countRunAndMakeAscending(TimSort.java:360) ~[?:?]
at java.util.TimSort.sort(TimSort.java:220) ~[?:?]
at java.util.Arrays.sort(Arrays.java:1307) ~[?:?]
at java.util.ArrayList.sort(ArrayList.java:1721) ~[?:?]
at org.apache.jmeter.sampler.DebugSampler.formatSet(DebugSampler.java:105) ~[ApacheJMeter_components.jar:5.6.2]
at org.apache.jmeter.sampler.DebugSampler.sample(DebugSampler.java:76) ~[ApacheJMeter_components.jar:5.6.2]
at org.apache.jmeter.threads.JMeterThread.doSampling(JMeterThread.java:651) ~[ApacheJMeter_core.jar:5.6.2]
at org.apache.jmeter.threads.JMeterThread.executeSamplePackage(JMeterThread.java:570) ~[ApacheJMeter_core.jar:5.6.2]
at org.apache.jmeter.threads.JMeterThread.processSampler(JMeterThread.java:501) [ApacheJMeter_core.jar:5.6.2]
at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:268) [ApacheJMeter_core.jar:5.6.2]
at java.lang.Thread.run(Thread.java:833) [?:?]