Continuous crawl in filesystem give NPE while deleting some files from the directory

On a continuous crawl for File system if some of the files are deleted from the directory the documents are not deleted from searchblox. There was a error in the manifoldcf.log

FATAL 2015-06-02 11:35:36,200 (Worker thread '7') - Error tossed: null
java.lang.NullPointerException
at org.apache.manifoldcf.agents.output.searchblox.SearchBloxConnector.removeDocument(SearchBloxConnector.java:381)
at org.apache.manifoldcf.agents.incrementalingest.IncrementalIngester.removeDocument(IncrementalIngester.java:2352)
at org.apache.manifoldcf.agents.incrementalingest.IncrementalIngester.documentDeleteMultiple(IncrementalIngester.java:1082)
at org.apache.manifoldcf.crawler.system.WorkerThread.removeFromIndex(WorkerThread.java:923)
at org.apache.manifoldcf.crawler.system.WorkerThread.processDeleteLists(WorkerThread.java:882)
at org.apache.manifoldcf.crawler.system.WorkerThread.run(WorkerThread.java:694)