Fix contributed upstream here:
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=42694.

Index: emacs-26.3/src/xfns.c
===================================================================
--- emacs-26.3.orig/src/xfns.c
+++ emacs-26.3/src/xfns.c
@@ -2628,6 +2628,8 @@ xic_free_xfontset (struct frame *f)
 static XIMStyle
 best_xim_style (XIMStyles *xim)
 {
+  if (xim == NULL) goto out;
+
   int i, j;
   int nr_supported = ARRAYELTS (supported_xim_styles);

@@ -2636,6 +2638,7 @@ best_xim_style (XIMStyles *xim)
       if (supported_xim_styles[i] == xim->supported_styles[j])
	return supported_xim_styles[i];

+ out:
   /* Return the default style.  */
   return XIMPreeditNothing | XIMStatusNothing;
 }
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<div class='path'>path: <a href='/guix/log/?id=d7885bbf071e19c6faa2b3fc7c07822682ffc2d9'>root</a>/<a href='/guix/log/gnu?id=d7885bbf071e19c6faa2b3fc7c07822682ffc2d9'>gnu</a>/<a href='/guix/log/gnu/packages?id=d7885bbf071e19c6faa2b3fc7c07822682ffc2d9'>packages</a>/<a href='/guix/log/gnu/packages/attr.scm?id=d7885bbf071e19c6faa2b3fc7c07822682ffc2d9'>attr.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/attr.scm?id=d7885bbf071e19c6faa2b3fc7c07822682ffc2d9&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-03-16 05:02:40 -0400'>2018-03-16</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=812cee6a07cb4b4ba4724768f9e745e2b25fe931'>gnu: attr: Use invoke instead of system*.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/attr.scm (attr)[arguments]: Use invoke.  Return a boolean from
all phase procedures.  Add a comment explaining why one call to system* is
retained.
</span></span></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-02-16 11:11:40 +0100'>2018-02-16</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=340978d7b054dcde6c3334267b40a8293eb0ce85'>gnu: Use HTTPS for supported nongnu.org home pages.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/acl.scm (acl)[home-page]: Use HTTPS.
* gnu/packages/admin.scm (dmidecode)[home-page]: Likewise.
* gnu/packages/attr.scm (attr)[home-page]: Likewise.
* gnu/packages/audio.scm (lash)[home-page]: Likewise.
* gnu/packages/avr.scm (avr-libc)[home-page]: Likewise.
* gnu/packages/backup.scm (rdiff-backup, libchop)[home-page]: Likewise.
* gnu/packages/compression.scm (fastjar, lzip, lziprecover, atool)
(lunzip, clzip, lzlib, plzip)[home-page]: Likewise.
* gnu/packages/emacs.scm (geiser, bbdb, m17n-lib, m17n-lib)[home-page]:
Likewise.
* gnu/packages/flashing-tools.scm (avrdude)[home-page]: Likewise.
* gnu/packages/fontutils.scm (libotf)[home-page]: Likewise.
* gnu/packages/game-development.scm (gzochi)[home-page]: Likewise.
* gnu/packages/games.scm (enigma)[home-page]: Likewise.
* gnu/packages/gsasl.scm (libntlm)[home-page]: Likewise.
* gnu/packages/gtk.scm (guile-cairo)[home-page]: Likewise.
* gnu/packages/guile.scm (guile-reader, guile-lib, guile-json)
(guile-redis, g-wrap)[home-page]: Likewise.
* gnu/packages/libunwind.scm (libunwind)[home-page]: Likewise.
* gnu/packages/lout.scm (lout)[home-page]: Likewise.
* gnu/packages/mpd.scm (sonata)[home-page]: Likewise.
* gnu/packages/networking.scm (quagga)[home-page]: Likewise.
* gnu/packages/ratpoison.scm (ratpoison)[home-page]: Likewise.
* gnu/packages/skribilo.scm (skribilo)[home-page]: Likewise.
* gnu/packages/telephony.scm (exosip)[home-page]: Likewise.
* gnu/packages/texinfo.scm (texi2html)[home-page]: Likewise.
* gnu/packages/xdisorg.scm (xbindkeys)[home-page]: Likewise.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>