AddressSanitizer: stack-use-after-scope in ScanContext::manageSeparator

==16708==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7fffffff8d82 at pc 0x7ffff6e9f382 bp 0x7fffffff8850 sp 0x7fffffff8000

READ of size 2 at 0x7fffffff8d82 thread T0

    #0 0x7ffff6e9f381  (/usr/local/lib64/libasan.so.4+0x76381)

    #1 0x7ffff0b598ad in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_replace(unsigned long, unsigned long, char const*, unsigned long) (/usr/local/lib64/libstdc++

.so.6+0x11e8ad)

    #2 0x13eeb54 in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::assign(char const*, unsigned long) /usr/local/include/c++/7.2.0/bits/basic_string.h:1371

    #3 0x13eeb54 in Collections::VB::ScanContext::manageSeparator(DocKey const&) /home/couchbase/server/kv_engine/engines/ep/src/collections/scan_context.cc:37

    #4 0x13473a7 in CouchKVStore::recordDbDump(_db*, _docinfo*, void*) /home/couchbase/server/kv_engine/engines/ep/src/couch-kvstore/couch-kvstore.cc:1750

    #5 0x1348ae7 in recordDbDumpC /home/couchbase/server/kv_engine/engines/ep/src/couch-kvstore/couch-kvstore.cc:61

...

Address 0x7fffffff8d82 is located in stack of thread T0 at offset 1202 in frame

    #0 0x13edc5d in Collections::VB::ScanContext::manageSeparator(DocKey const&) /home/couchbase/server/kv_engine/engines/ep/src/collections/scan_context.cc:24

  This frame has 19 object(s):

    [32, 33) '<unknown>'

    [96, 97) '<unknown>'

    [160, 161) '<unknown>'

    [224, 232) '<unknown>'

    [288, 296) '<unknown>'

    [352, 368) '<unknown>'

    [416, 432) '<unknown>'

    [480, 496) '<unknown>'

    [544, 560) '<unknown>'

    [608, 624) '<unknown>'

    [672, 688) '<unknown>'

    [736, 752) '<unknown>'

    [800, 816) '<unknown>'

    [864, 880) '<unknown>'

    [928, 944) '<unknown>'

    [992, 1016) 'cKey'

    [1056, 1080) 'cKey2'

    [1120, 1144) '<unknown>'

    [1184, 1216) '<unknown>' <== Memory access at offset 1202 is inside this variable