Comment 2 for bug 1664760

Thread 4 "Mir/Comp" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffecac3700 (LWP 11311)]
0x00007ffff5cc0150 in mir::compositor::TemporaryBuffer::size (
    this=0x7fffe80084f0)
    at /home/dan/bzr/mir/trunk/src/server/compositor/temporary_buffers.cpp:60
60 return buffer->size();
(gdb) bt
#0 0x00007ffff5cc0150 in mir::compositor::TemporaryBuffer::size (
    this=0x7fffe80084f0)
    at /home/dan/bzr/mir/trunk/src/server/compositor/temporary_buffers.cpp:60
#1 0x00007ffff5e2d98c in mir::gl::tessellate_renderable_into_rectangle (
    renderable=..., offset=...)
    at /home/dan/bzr/mir/trunk/src/gl/tessellation_helpers.cpp:29
#2 0x00007ffff5e25f8f in mir::renderer::gl::Renderer::tessellate (
    this=0x7fffe80008c0,
    primitives=std::vector of length 1, capacity 1 = {...}, renderable=...)
    at /home/dan/bzr/mir/trunk/src/renderers/gl/renderer.cpp:200
#3 0x00007ffff5e264f4 in mir::renderer::gl::Renderer::draw (
    this=0x7fffe80008c0, renderable=..., prog=...)
    at /home/dan/bzr/mir/trunk/src/renderers/gl/renderer.cpp:253
#4 0x00007ffff5e26182 in mir::renderer::gl::Renderer::render (
    this=0x7fffe80008c0,
    renderables=std::vector of length 4, capacity 4 = {...})
    at /home/dan/bzr/mir/trunk/src/renderers/gl/renderer.cpp:213
#5 0x00007ffff5cbddd8 in mir::compositor::DefaultDisplayBufferCompositor::composite(std::vector<std::shared_ptr<mir::compositor::SceneElement>, std::allocator<std::shared_ptr<mir::compositor::SceneElement> > >&&) (this=0x7fffe8008620,
    scene_elements=<unknown type in /home/dan/bzr/mir/trunk/build/bin/../lib/libmirserver.so.44, CU 0x66b90b, DIE 0x673525>)
    at /home/dan/bzr/mir/trunk/src/server/compositor/default_display_buffer_compositor.cpp:84
#6 0x00007ffff5cc5798 in mir::compositor::CompositingFunctor::operator() (
    this=0x5555559ded70)
    at /home/dan/bzr/mir/trunk/src/server/compositor/multi_threaded_compositor.cpp:141
#7 0x00007ffff5cc8fc0 in std::_Function_handler<void (), std::reference_wrapper<mir::compositor::CompositingFunctor> >::_M_invoke(std::_Any_data const&) (
    __functor=...) at /usr/include/c++/6/functional:1761
#8 0x00007ffff5b6a9f6 in std::function<void ()>::operator()() const (
    this=0x7fffecac2d80) at /usr/include/c++/6/functional:2127