java.lang.NullPointerException from _revs_diff request

Under system test load during the rebalance phase the following errors start to appear in the elastic search node.

system is under a frontend load of 10k ops, 70% sets while 4 nodes rebalanced out.

AsyncHttpConnection@3a726c77,g=HttpGenerator

{s=3,h=-111,b=368,c=-1},p=HttpParser{s=0,l=15,c=160176},r=5
[2013-02-19 22:38:17,727][WARN ][org.eclipse.jetty.server.AsyncHttpConnection] Closing EndPoint making no progress: 200 SCEP@50b22257{l(/10.3.2.115:49816)<->r(/10.1.3.250:9091),d=true,open=true,ishut=false,oshut=false,rb=false,wb=false,w=false,i=5r}-{AsyncHttpConnection@3a726c77,g=HttpGenerator{s=3,h=-111,b=368,c=-1}

,p=HttpParser

{s=0,l=15,c=160176},r=5} AsyncHttpConnection@3a726c77,g=HttpGenerator{s=3,h=-111,b=368,c=-1},p=HttpParser{s=0,l=15,c=160176}

,r=5
[2013-02-19 22:42:02,537][WARN ][org.eclipse.jetty.servlet.ServletHandler] /default%2f608%3b00000000000000000000000000000000/_revs_diff
java.lang.NullPointerException
at org.elasticsearch.transport.couchbase.capi.ElasticSearchCAPIBehavior.revsDiff(ElasticSearchCAPIBehavior.java:150)
at com.couchbase.capi.servlet.CAPIServlet.handleRevsDiff(CAPIServlet.java:180)
at com.couchbase.capi.servlet.CAPIServlet.service(CAPIServlet.java:78)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:594)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:485)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:486)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:233)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1065)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:412)