NPE is thrown when the value of the field whose type is int64 (logicalType - timestamp), is null

[rahul-aravind-opti]

ProtobufData#fromConnectData throws NullPointerException if the int64 (logical Timestamp type) field's value is null.

org.apache.kafka.connect.errors.ConnectException: Tolerance exceeded in error handler
        at org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndHandleError(RetryWithToleranceOperator.java:178)
        at org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execute(RetryWithToleranceOperator.java:104)
        at org.apache.kafka.connect.runtime.WorkerSourceTask.convertTransformedRecord(WorkerSourceTask.java:284)
        at org.apache.kafka.connect.runtime.WorkerSourceTask.sendRecords(WorkerSourceTask.java:309)
        at org.apache.kafka.connect.runtime.WorkerSourceTask.execute(WorkerSourceTask.java:234)
        at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:177)
        at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:227)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
        at org.apache.kafka.connect.data.Timestamp.fromLogical(Timestamp.java:51)
        at com.blueapron.connect.protobuf.ProtobufData.fromConnectData(ProtobufData.java:452)
        at com.blueapron.connect.protobuf.ProtobufData.fromConnectData(ProtobufData.java:418)
        at com.blueapron.connect.protobuf.ProtobufConverter.fromConnectData(ProtobufConverter.java:60)
        at org.apache.kafka.connect.runtime.WorkerSourceTask.lambda$convertTransformedRecord$2(WorkerSourceTask.java:284)
        at org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndRetry(RetryWithToleranceOperator.java:128)
        at org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndHandleError(RetryWithToleranceOperator.java:162)
        ... 11 more

Looks like we have to ignore setting the field descriptor for the fields whose values are null.