If the only surface in a session cannot take focus the server crashes

I'm impressed you have a 14 year old system working. Does that mean you use radeon/nouveau and not intel graphics on it? (I can only get up to 9 year old Intel GPUs working with Mir, and 6 years old working with Unity8)

Fix committed to lp:mir/0.26 at revision 4033, scheduled for release in Mir 0.26.2

Fix committed into lp:mir at revision None, scheduled for release in mir, milestone 1.0.0

This bug was fixed in the package miral - 1.3.0+17.04.20170303-0ubuntu1

---------------
miral (1.3.0+17.04.20170303-0ubuntu1) zesty; urgency=medium

  * New upstream release 1.3.0 (https://launchpad.net/miral/+milestone/1.3)

    - ABI summary:
      . miral ABI unchanged at 2
    - Enhancements:
      . [libmiral] Support for workspaces
      . [libmiral] Add miral::WindowManagerTools::focus_prev_within_application
                   (LP: #1668562)
      . [libmirclientcpp] A better description of libmirclientcpp-dev
      . [libmirclientcpp] Add RAII wrapper for MirDisplayConfig.
      . [libmirclientcpp] Prevent accidental double-release by deleting release
                          functions for handle classes
      . [miral-shell] Example workspaces implementation
      . [miral-shell] Use background to show keyboard shortcuts
    - Bugs fixed:
      . [libmiral] Join internal client threads before server shutdown
                   (LP: #1668651)
      . [miral-shell] Workaround for crash on exit (LP: #1667645)

 -- Alan Griffiths <email address hidden> Fri, 03 Mar 2017 10:19:14 +0000

This bug was fixed in the package mir - 0.26.2+17.04.20170322.1-0ubuntu1

---------------
mir (0.26.2+17.04.20170322.1-0ubuntu1) zesty; urgency=medium

  [ Daniel van Vugt ]
  * New upstream release 0.26.2 (https://launchpad.net/mir/+milestone/0.26.2)
    - Bugs fixed:
      . EDID does not change when hotplugging a monitor (LP: #1660017)
      . [regression] mirout crashes when connecting to unity8 or any nested
        server: [libprotobuf FATAL /usr/include/google/protobuf/repeated_field.
        h:1408] CHECK failed: (index) < (current_size_) (LP: #1661163)
      . Mir server crashed with SIGSEGV in
        mir::compositor::TemporaryBuffer::size() called from
        mir::gl::tessellate_renderable_into_rectangle() (LP: #1664760)
      . Nested servers (Unity8) periodically stutter (half frame rate) with
        Mir 0.26.1 (LP: #1666372)
      . Don't dereference the end iterator in ms::ApplicationSession::
        surface_after() (LP: #1667645)
      . [regression] OSK input shaping no longer works correctly (LP: #1669444)
      . Setting MirWindowSpec parameters always causes window's input_region
        to be reset (LP: #1670876)
      . Subpixel order not included in Mir display information (LP: #1393578)
      . Presentation chains should support various swap interval modes
        (LP: #1673533)
      . Need an extension for GBM buffers to replace
        mir_buffer_get_buffer_package() (LP: #1673534)
      . Seg fault on detect_fd_leaks (LP: #1661498)

 -- Cemil Azizoglu <email address hidden> Wed, 22 Mar 2017 04:54:19 +0000