bug#38081: 27.0.50; compilation-error-properties error if file is nil

[noah <noah.v.peart@gmail.com>]

If the FILE argument in `compilation-error-regexp-alist-alist`
is a function that returns nil on a matched line, then
`compilation-error-properties` throws an error when trying to
do a `string-match` against FILE and elements in
`compilation-transform-file-match-alist`.

It seems like there should be a check that the FILE is in fact
non-nil.

Quick recipe that should reproduce the error:

    (require 'compile)

    ;; function that is supposed to find appropriate file name
    (defun my-determine-file-name ())

    (define-compilation-mode my-mode "MM"
      (setq-local compilation-error-regexp-alist '(my-err))
      (setq-local compilation-error-regexp-alist-alist
                  '((my-err "\\([0-9]+\\):\\([0-9]+\\)"
                            my-determine-file-name 1 2))))

    (compilation-start "echo -e 1:2\n3:4" 'my-mode)



In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2019-11-03 built on noah-M51AC
Repository revision: 58fde6362f88e1d943ae033bda31becc67892112
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Ubuntu 18.04.3 LTS

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Mark set
eval-buffer: Symbol’s function definition is void: define-compilation-modeError during redisplay: (jit-lock-function 1) signaled (wrong-type-argument stringp nil)
error in process filter: compilation-error-properties: Wrong type argument: stringp, nil
error in process filter: Wrong type argument: stringp, nil
MM exited abnormally with code 127
Error during redisplay: (jit-lock-function 94) signaled (wrong-type-argument stringp nil)

Configured using:
 'configure --prefix=/usr/local --with-modules --with-xwidgets'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GSETTINGS GLIB NOTIFY INOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS XWIDGETS JSON
PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa epg
epg-config gnus-util rmail rmail-loaddefs text-property-search time-date
subr-x seq byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
derived compile comint ansi-color ring tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting xwidget-internal move-toolbar
gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 51286 8879)
 (symbols 48 6525 1)
 (strings 32 16944 1873)
 (string-bytes 1 566370)
 (vectors 16 10791)
 (vector-slots 8 136891 11084)
 (floats 8 21 41)
 (intervals 56 293 6)
 (buffers 1000 12))