NullPointerException (Text.java:388)

[Vitaliy Semochkin]

Hi,

during map phase I recieved following expcetion

java.lang.NullPointerException
        at org.apache.hadoop.io.Text.encode(Text.java:388)
        at org.apache.hadoop.io.Text.encode(Text.java:369)
        at org.apache.hadoop.io.Text.writeString(Text.java:409)
        at org.apache.hadoop.mapreduce.Counter.write(Counter.java:77)
        at org.apache.hadoop.mapred.Counters$Group.write(Counters.java:311)
        at org.apache.hadoop.mapred.Counters.write(Counters.java:491)
        at org.apache.hadoop.mapred.TaskStatus.write(TaskStatus.java:370)
        at 
org.apache.hadoop.io.ObjectWritable.writeObject(ObjectWritable.java:159)
        at org.apache.hadoop.ipc.RPC$Invocation.write(RPC.java:112)
        at org.apache.hadoop.ipc.Client$Connection.sendParam(Client.java:475)
        at org.apache.hadoop.ipc.Client.call(Client.java:721)
        at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:220)
        at org.apache.hadoop.mapred.$Proxy0.statusUpdate(Unknown Source)
        at org.apache.hadoop.mapred.Task.statusUpdate(Task.java:705)
        at org.apache.hadoop.mapred.Task.sendLastUpdate(Task.java:729)
        at org.apache.hadoop.mapred.Task.done(Task.java:695)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:309)
        at org.apache.hadoop.mapred.Child.main(Child.java:170)

from the stack trace I see that the exception happens in hadoop code

encode(Text.java:388) -  ByteBuffer bytes =
encoder.encode(CharBuffer.wrap(string.toCharArray()));

I guess string was null, but what could cause such argument during map?
Can it be an empty file or emtpy line?

Thanks in Advance,
Vitaliy S