Crash in fdb_close() during bucket deletion

During bucket deletion in ep-engine, prior to call fdb_shutdown, each shard file in ForestKVStore instance is closed using fdb_close. A crash is observed during fdb_close. Stack trace given below. Full trace is attached.

Thread 21 Crashed:
0 libjemalloc.2.dylib 0x0000000103e92de0 ifree + 256
1 libjemalloc.2.dylib 0x0000000103e93095 je_free + 133
2 libforestdb.dylib 0x0000000105041f21 btreeblk_free + 257 (btreeblock.cc:1359)
3 libforestdb.dylib 0x0000000105050813 _fdb_close + 67 (forestdb.cc:6340)
4 libforestdb.dylib 0x000000010505034d _fdb_close_root + 93 (forestdb.cc:6319)
5 libforestdb.dylib 0x0000000105056341 fdb_close + 81 (forestdb.cc:6289)
6 ep.dylib 0x0000000104ae180f ForestKVStore::shutdownForestDb() + 15 (locks.h:71)
7 ep.dylib 0x0000000104ae3c83 ForestKVStore::~ForestKVStore() + 867 (forest-kvstore.cc:199)
8 ep.dylib 0x0000000104ae3e8e ForestKVStore::~ForestKVStore() + 14 (forest-kvstore.cc:163)
9 ep.dylib 0x0000000104a98ae9 KVShard::~KVShard() + 153 (kvstore.h:316)
10 ep.dylib 0x0000000104ac1ffe VBucketMap::~VBucketMap() + 110 (vbucketmap.cc:56)
11 ep.dylib 0x0000000104a7ce51 EventuallyPersistentEngine::~EventuallyPersistentEngine() + 33 (ep_engine.cc:6342)
12 ep.dylib 0x0000000104a6782a EvpDestroy(engine_interface*, bool) + 106 (ep_engine.cc:144)
13 memcached 0x0000000103dc85f9 delete_bucket_main(void*) + 1225 (memcached.cc:2462)
14 libplatform.0.1.0.dylib 0x0000000103f766ed platform_thread_wrap + 29 (cb_pthreads.c:24)
15 libsystem_pthread.dylib 0x00007fff88c1805a _pthread_body + 131
16 libsystem_pthread.dylib 0x00007fff88c17fd7 _pthread_start + 176
17 libsystem_pthread.dylib 0x00007fff88c153ed thread_start + 13