Crawling from REST API giving NullPointerException

Crawling is not working from REST API.

Steps to reproduce.
-----------------------
1. Start the Nutch server (port 9000).
2. Submit the PUT request , to create/initiate crawl job.
eg:
URL: http://localhost:9000/nutch/jobs
HTTP METHOD: PUT
Content:
{
"crawl":"123",
"type":"crawl",
"conf":"default",
"args":

{ "class":"org.apache.nutch.crawl.Crawler", "seed":"http://www.somesite.com", "seedDir":"runtime/local/url/url.txt", "depth":2 }

}
3. Getting the following exception in Generator phase.
2014-05-13 11:37:57,863 WARN mapred.LocalJobRunner (LocalJobRunner.java:run(435)) - job_local1326997137_0002
java.lang.NullPointerException
at org.apache.avro.util.Utf8.<init>(Utf8.java:37)
at org.apache.nutch.crawl.GeneratorReducer.setup(GeneratorReducer.java:100)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:174)
at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:649)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:418)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:398)