Assertion failure in btree::btree_node::construct_value

[smccauliff]

This appears to be from this line:
assert(memcmp(zero_value, v, sizeof(value_type)) == 0);

If a new value is being constructed why should it be zero initalized? Commenting out this assert causes segv later in the program.

__GI_raise 0x00007fedd5098f47
__GI_abort 0x00007fedd509a8b1
__assert_fail_base 0x00007fedd508a42a
__GI___assert_fail 0x00007fedd508a4a2
btree::btree_node<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> >::construct_value<std::pair<unsigned long const, app::MessageAndCoverCount> > btree.h:881
btree::btree_node<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> >::construct_value<std::pair<unsigned long const, app::MessageAndCoverCount> > btree.h:894
btree::btree_node<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> >::move_value btree.h:615
btree::btree_node<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> >::rebalance_right_to_left btree.h:1819
btree::btree<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> >::rebalance_or_split btree.h:2351
btree::btree<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> >::internal_emplace<std::piecewise_construct_t const&, std::tuple<unsigned long const&>, std::tuple<> >(btree::btree_iterator<btree::btree_node<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> > const, std::pair<unsigned long const, app::MessageAndCoverCount> const&, std::pair<unsigned long const, app::MessageAndCoverCount> const*>, std::piecewise_construct_t const&, std::tuple<unsigned long const&>&&, std::tuple<>&&) btree.h:2559
btree::btree<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> >::emplace_unique_key_args<std::piecewise_construct_t const&, std::tuple<unsigned long const&>, std::tuple<> >(unsigned long const&, std::piecewise_construct_t const&, std::tuple<unsigned long const&>&&, std::tuple<>&&) btree.h:2122
btree::btree_map_container<btree::btree<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> > >::try_emplace<>(unsigned long const&) map.h:70
btree::btree_map_container<btree::btree<btree::btree_map_params<unsigned long, app::MessageAndCoverCount, std::less, std::allocator<std::pair<unsigned long const, app::MessageAndCoverCount> >, 256> > >::operator[] map.h:118
app::CacheTest::PopulateCache test_cache.cpp:218