Also on a separate boot, an almost identical stacktrace from unity8 this time:

Core was generated by `unity8'.
Program terminated with signal SIGABRT, Aborted.
#0  __libc_do_syscall ()
    at ../ports/sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:44
#1  0xb620a05e in __GI_raise (sig=sig@entry=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#2  0xb620ad4e in __GI_abort () at abort.c:89
#3  0xb62052b8 in __assert_fail_base (
    fmt=0x1 <error: Cannot access memory at address 0x1>, 
    assertion=0xb437d0f4 "!pending_client_notifications.empty()", 
    assertion@entry=0x0, 
    file=0xb437cff0 "/build/buildd/mir-0.5.0+14.10.20140722/src/server/compositor/buffer_queue.cpp", file@entry=0xb4612220 "\001", line=136, 
    line@entry=3056369844, 
    function=function@entry=0xb437ccf4 <mir::compositor::BufferQueue::BufferQueue(int, std::shared_ptr<mir::graphics::GraphicBufferAllocator> const&, mir::graphics::BufferProperties const&, mir::compositor::FrameDroppingPolicyFactory const&)::{lambda()#1}::operator()() const::__PRETTY_FUNCTION__> "mir::compositor::BufferQueue::BufferQueue(int, const std::shared_ptr<mir::graphics::GraphicBufferAllocator>&, const mir::graphics::BufferProperties&, const mir::compositor::FrameDroppingPolicyFactory&"...) at assert.c:92
#4  0xb620534e in __GI___assert_fail (assertion=0x0, file=0xb4612220 "\001", 
    line=3056369844, 
    function=0xb437ccf4 <mir::compositor::BufferQueue::BufferQueue(int, std::shared_ptr<mir::graphics::GraphicBufferAllocator> const&, mir::graphics::BufferProperties const&, mir::compositor::FrameDroppingPolicyFactory const&)::{lambda()#1}::operator()() const::__PRETTY_FUNCTION__> "mir::compositor::BufferQueue::BufferQueue(int, const std::shared_ptr<mir::graphics::GraphicBufferAllocator>&, const mir::graphics::BufferProperties&, const mir::compositor::FrameDroppingPolicyFactory&"...) at assert.c:101
#5  0xb42dff6a in operator() (__closure=0xb62c80b4 <lock>)
    at /build/buildd/mir-0.5.0+14.10.20140722/src/server/compositor/buffer_queue.cpp:136
#6  std::_Function_handler<void(), mir::compositor::BufferQueue::BufferQueue(int, const std::shared_ptr<mir::graphics::GraphicBufferAllocator>&, const mir::graphics::BufferProperties&, const mir::compositor::FrameDroppingPolicyFactory&)::<lambda()> >::_M_invoke(const std::_Any_data &) (__functor=...)
    at /usr/include/c++/4.9/functional:2039
#7  0xb42deeec in operator() (this=0x9d71b77c)
    at /usr/include/c++/4.9/functional:2439
#8  operator() (__closure=0x9d71b778)
    at /build/buildd/mir-0.5.0+14.10.20140722/src/server/compositor/timeout_frame_dropping_policy_factory.cpp:59
#9  std::_Function_handler<void(), (anonymous namespace)::TimeoutFrameDroppingPolicy::TimeoutFrameDroppingPolicy(const std::shared_ptr<mir::time::Timer>&, std::chrono::milliseconds, std::function<void()>)::<lambda()> >::_M_invoke(const std::_Any_data &) (__functor=...) at /usr/include/c++/4.9/functional:2039
#10 0xb42c65ac in operator() (ec=..., __closure=<optimized out>)
    at /build/buildd/mir-0.5.0+14.10.20140722/src/server/asio_main_loop.cpp:390
#11 std::_Function_handler<void(const boost::system::error_code&), (anonymous namespace)::make_handler(std::weak_ptr<(anonymous namespace)::AlarmImpl::InternalState>)::<lambda(const boost::system::error_code&)> >::_M_invoke(const std::_Any_data &, const boost::system::error_code &) (__functor=..., __args#0=...)
    at /usr/include/c++/4.9/functional:2039
#12 0xb42cbb20 in operator() (__args#0=..., this=0xbef19224)
    at /usr/include/c++/4.9/functional:2439
#13 operator() (this=0xbef19224)
    at /usr/include/boost/asio/detail/bind_handler.hpp:47
#14 asio_handler_invoke<boost::asio::detail::binder1<std::function<void(const boost::system::error_code&)>, boost::system::error_code> > (function=...)
    at /usr/include/boost/asio/handler_invoke_hook.hpp:69
#15 invoke<boost::asio::detail::binder1<std::function<void(const boost::system::error_code&)>, boost::system::error_code>, std::function<void(const boost::system::error_code&)> > (context=..., function=...)
    at /usr/include/boost/asio/detail/handler_invoke_helpers.hpp:37
#16 boost::asio::detail::wait_handler<std::function<void (boost::system::error_code const&)> >::do_complete(boost::asio::detail::task_io_service*, boost::asio::detail::task_io_service_operation*, boost::system::error_code const&, unsigned int) (owner=0x88, base=<optimized out>)
    at /usr/include/boost/asio/detail/wait_handler.hpp:70
#17 0xb42ca2f6 in complete (bytes_transferred=<optimized out>, ec=..., 
    owner=..., this=0xa70e92d8)
    at /usr/include/boost/asio/detail/task_io_service_operation.hpp:38
#18 do_run_one (ec=..., this_thread=..., lock=..., this=0x1da6b90)
    at /usr/include/boost/asio/detail/impl/task_io_service.ipp:384
#19 boost::asio::detail::task_io_service::run (this=0x1da6b90, ec=...)
    at /usr/include/boost/asio/detail/impl/task_io_service.ipp:153
#20 0xb42c6404 in run (this=<optimized out>)
    at /usr/include/boost/asio/impl/io_service.ipp:59
#21 mir::AsioMainLoop::run (this=<optimized out>)
    at /build/buildd/mir-0.5.0+14.10.20140722/src/server/asio_main_loop.cpp:261
#22 0xb42bf91e in mir::DisplayServer::run (this=this@entry=0xbef19358)
    at /build/buildd/mir-0.5.0+14.10.20140722/src/server/display_server.cpp:223
#23 0xb42bd434 in mir::run_mir(mir::ServerConfiguration&, std::function<void (mir::DisplayServer&)>) (config=..., init=...)
    at /build/buildd/mir-0.5.0+14.10.20140722/src/server/run_mir.cpp:93
#24 0xb4409ee6 in QMirServer::runWithClient(std::function<int (int, char const**, ShellServerConfiguration*)>) ()
   from /usr/lib/arm-linux-gnueabihf/libunity-mir.so.1
#25 0xb440a100 in runQMirServerWithClient ()
   from /usr/lib/arm-linux-gnueabihf/libunity-mir.so.1
#26 0x00013f5a in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)