bug#31236: [PATCH] Fix pre- and post-command-hook errors in term.el

[Karl Otness]

As far as I can tell there isn't an existing bug report for this
issue. It is very minor but I have attached a fix. This affects Emacs
26.1-rc1 `term' and `ansi-term'. In char mode term installs functions
in both pre- and post-command-hooks. After the process exits both of
these hooks produce errors and then are removed by Emacs after
printing a message.

Both of these hooks are re-installed when entering char mode and
removing them if they are not present will do nothing. To produce this
change, I took the remove-hook lines used when entering line mode and
placed them in `term-handle-exit'.

To reproduce the issue in 26.1, M-x term, exit the running process and
execute any command (i.e. move point). In *Messages* there should be
the following lines:

Error in pre-command-hook (term-set-goto-process-mark):
(wrong-type-argument processp nil)
Error in post-command-hook (term-goto-process-mark-maybe):
(wrong-type-argument processp nil)

The error seems to come up from `process-mark'. After this change,
these errors no longer appear as the hooks are removed. I have
attached a patch which applies this change to current master.

Thank you,
Karl

0001-Fix-pre-and-post-command-hook-errors-in-term.el.patch
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