Check if the process-mark is non-nil and if mark-pos is non-nil to prevent errors

See merge request qhong/crdt.el!1

** DONE Track authorship in-buffer via properties
   ~crdt-visualize-author-mode~ UI
** DONE Make interactive changes to crdt-version and crdt-connect
** DONE Stop leaking ip address
** DONE Investigate why xref-find-definitions causes error
** DONE Figure out the code for colouring selection colours from
   ‘default’s :background

- gracefully degrade when TLS handshake fail (I hope it works)
- remove session name settings

also remove some debug printing

commit a80f73d8
Merge: 20ff83c8 2eddf967
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Oct 1 15:34:50 2021 -0700

    Merge branch 'master' of code.librehq.com:qhong/crdt.el

commit 20ff83c8
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Oct 1 15:34:07 2021 -0700

    fix a bug in buffer remove handler

commit 52506c63
Author: Qiantan Hong <qhong@mit.edu>
Date:   Thu Sep 30 10:01:16 2021 -0700

    bump version

commit 43bbb18b
Author: Qiantan Hong <qhong@mit.edu>
Date:   Tue Sep 28 00:02:12 2021 -0700

    fix a bug when synchronizing mark

commit 4b86674f
Author: Qiantan Hong <qhong@mit.edu>
Date:   Sat Sep 25 11:48:43 2021 -0700

    more sensible version message

commit 270a4099
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 23:17:15 2021 -0700

    return -> cl-return

commit 709059ff
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 22:54:09 2021 -0700

    fix disconnect warn condition

commit 102498e8
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 22:51:48 2021 -0700

    remove tramp for now, keep it simple

commit 94b0c488
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 21:07:13 2021 -0700

    bump version number

commit fae016ba
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 21:06:19 2021 -0700

    Preliminary url support

commit 38fdfc55
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 20:18:57 2021 -0700

    semver, and various fixes

commit 97427622
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 16:29:12 2021 -0700

    fix bug in crdt--stop-session interactive spec

commit d46be729
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 16:26:44 2021 -0700

    remove base64 mangling and fix a stupid bug

    IDK why base64 was there.
    stupid bug: typo overlay-mode should be overlay-move

commit 1347c678
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 15:19:50 2021 -0700

    Use some warning instead of message

commit 5d90bf0c
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 12:33:42 2021 -0700

    generate uninteresting process buffers instead

commit 4b86674f
Author: Qiantan Hong <qhong@mit.edu>
Date:   Sat Sep 25 11:48:43 2021 -0700

    more sensible version message

commit 270a4099
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 23:17:15 2021 -0700

    return -> cl-return

commit 709059ff
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 22:54:09 2021 -0700

    fix disconnect warn condition

commit 102498e8
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 22:51:48 2021 -0700

    remove tramp for now, keep it simple

commit 94b0c488
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 21:07:13 2021 -0700

    bump version number

commit fae016ba
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 21:06:19 2021 -0700

    Preliminary url support

commit 38fdfc55
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 20:18:57 2021 -0700

    semver, and various fixes

commit 97427622
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 16:29:12 2021 -0700

    fix bug in crdt--stop-session interactive spec

commit d46be729
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 16:26:44 2021 -0700

    remove base64 mangling and fix a stupid bug

    IDK why base64 was there.
    stupid bug: typo overlay-mode should be overlay-move

commit 1347c678
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 15:19:50 2021 -0700

    Use some warning instead of message

commit 5d90bf0c
Author: Qiantan Hong <qhong@mit.edu>
Date:   Fri Sep 24 12:33:42 2021 -0700

    generate uninteresting process buffers instead

IDK why base64 was there.
stupid bug: typo overlay-mode should be overlay-move