Memcached crash after bucket deletion on 181

Core was generated by `/opt/couchbase/bin/memcached -X /opt/couchbase/lib/memcached/stdin_term_handler'.
Program terminated with signal 6, Aborted.
#0 0x0000003171230265 in raise () from /lib64/libc.so.6
(gdb) t a a bt

Thread 1 (Thread 0x4bf06940 (LWP 8334))
#0 0x0000003171230265 in raise () from /lib64/libc.so.6
#1 0x0000003171231d10 in abort () from /lib64/libc.so.6
#2 0x00000031712296e6 in __assert_fail () from /lib64/libc.so.6
#3 0x00002aaaaaaada12 in engine_shutdown_thread (arg=0x1ea71500) at bucket_engine.c:1327
#4 0x0000000021e8c718 in ?? ()
#5 0x000000004bf05fe0 in ?? ()
#6 0x00002aaaaad60539 in TapConnection::opaqueCmdToString (opaque_code=8127) at tapconnection.cc:60
#7 0x000000002cb7e000 in ?? ()
#8 0x00002aaaaad71ae1 in idle_UNLOCKED (this=0x31842e9420, cookie=0x31842e9438, name="Reaping tap connection: eq_tapq:replication_ns_1@10.1.3.74", flags=0, backfillAge=1274043952, tapKeepAlive=0) at tapconnection.hh:677
#9 idle (this=0x31842e9420, cookie=0x31842e9438, name="Reaping tap connection: eq_tapq:replication_ns_1@10.1.3.74", flags=0, backfillAge=1274043952, tapKeepAlive=0) at tapconnection.hh:682
#10 TapConnMap::newProducer (this=0x31842e9420, cookie=0x31842e9438, name="Reaping tap connection: eq_tapq:replication_ns_1@10.1.3.74", flags=0, backfillAge=1274043952, tapKeepAlive=0) at tapconnmap.cc:249
#11 0x00000031842e6630 in vtable for std::ios_base () from /usr/lib64/libstdc++.so.6
#12 0x0000000000000006 in ?? ()
#13 0x0000000000000000 in ?? ()