Rebalance failure because of an assertion failure

http://qa.hq.northscale.net/job/centos_x64--107_02--rebalanceXDCR_SSL-P1/10/

On 10.5.2.229, core.memcached.30369, that shows the assertion fail:

#0 0x00007f0204bc98a5 in raise () from /lib64/libc.so.6
#1 0x00007f0204bcb085 in abort () from /lib64/libc.so.6
#2 0x00007f0204bc2a1e in __assert_fail_base () from /lib64/libc.so.6
#3 0x00007f0204bc2ae0 in __assert_fail () from /lib64/libc.so.6
#4 0x00007f01fdf227a1 in PassiveStream::~PassiveStream (this=0x85bae00, __in_chrg=<value optimized out>) at /home/buildbot/centos-5-x64-300-builder/build/build/ep-engine/src/upr-stream.cc:847
#5 0x00007f01fdf14845 in UprConsumer::processBufferedItems (this=0x6e45340) at /home/buildbot/centos-5-x64-300-builder/build/build/ep-engine/src/atomic.h:397
#6 0x00007f01fdf148fa in Processer::run (this=0x25af8d0) at /home/buildbot/centos-5-x64-300-builder/build/build/ep-engine/src/upr-consumer.cc:48
#7 0x00007f01fdee7d11 in ExecutorThread::run (this=0x25ac510) at /home/buildbot/centos-5-x64-300-builder/build/build/ep-engine/src/executorthread.cc:94
#8 0x00007f01fdee8236 in launch_executor_thread (arg=0x76a1) at /home/buildbot/centos-5-x64-300-builder/build/build/ep-engine/src/executorthread.cc:33
#9 0x00007f0206d29b6f in platform_thread_wrap (arg=0x2560bd0) at /home/buildbot/centos-5-x64-300-builder/build/build/platform/src/cb_pthreads.c:19
#10 0x00007f0205add851 in start_thread () from /lib64/libpthread.so.0
#11 0x00007f0204c7f90d in clone () from /lib64/libc.so.6