bug#39178: 27.0.50; [PATCH] Fix: gdb-mi cannot recover from handler function error

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Sat, 18 Jan 2020 13:48:45 -0500
> 
> If a handler produces an error, cleanup code doesn’t get to run and leaves 
> gbd-mi.el in a corrupted state (in terms of communication buffer). So other 
> handlers can’t parse the message sent from gdb anymore.

Thanks, pushed to the emacs-27 branch.

Please in the future try to observe the following nits:

> * lisp/progmodes/gdb-mi.el (gdb-handle-reply):
> Handle error in ’handler-function’ so the cleanup code after it

Please use quoting 'like this' in log messages (and also in NEWS).

> +      (condition-case err
> +          ;; protect against errors in handler-function

Comments should be complete sentences, and as such, begin with a
capital letter and end in a period.

(I fixed all of these nits this time.)