title: SerializationException: Error serializing Avro message
body: <p>I'm using KStreams which have a AVRO schema and are hooked up with the schema registry. When I start processing the stream, I get a <code>NullPointerException</code> as follows:</p>
  
  <pre><code>Caused by: org.apache.kafka.common.errors.SerializationException: Error serializing Avro message
  Caused by: java.lang.NullPointerException: null of int in field SCORE_THRSHLD_EXCD of gbl_au_avro
      at org.apache.avro.generic.GenericDatumWriter.npe(GenericDatumWriter.java:145)
      at org.apache.avro.generic.GenericDatumWriter.writeWithoutConversion(GenericDatumWriter.java:139)
      at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:75)
      at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:62)
      at io.confluent.kafka.serializers.AbstractKafkaAvroSerializer.serializeImpl(AbstractKafkaAvroSerializer.java:92)
      at io.confluent.kafka.serializers.KafkaAvroSerializer.serialize(KafkaAvroSerializer.java:53)
      at io.confluent.kafka.streams.serdes.avro.GenericAvroSerializer.serialize(GenericAvroSerializer.java:63)
      at io.confluent.kafka.streams.serdes.avro.GenericAvroSerializer.serialize(GenericAvroSerializer.java:39)
      at org.apache.kafka.streams.processor.internals.RecordCollectorImpl.send(RecordCollectorImpl.java:154)
      at org.apache.kafka.streams.processor.internals.RecordCollectorImpl.send(RecordCollectorImpl.java:98)
      at org.apache.kafka.streams.processor.internals.SinkNode.process(SinkNode.java:89)
      at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143)
      at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:126)
      at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:90)
  </code></pre>
  
  <p>Not sure what the issue is here. Both source and sink have schema repository linked to them and have schemas defined correctly.</p>
  
  <p>Can you please suggest what I might be doing wrong?</p>