Fix crash condition when an X server connection is broken. (Reported by Vincent Bernat.)

* src/xterm.c (x_flush): Return immediately when redisplay is inhibited.

git-archimport-id: lorentey@elte.hu--2004/emacs--multi-tty--0--patch-304

README.multi-tty

@@ -32,6 +32,7 @@ contributed to the project by testing, submitting patches, bug
 reports, and suggestions.  Thanks!
 
 ARISAWA Akihiro <ari at mbf dot ocn dot ne dot jp>
+Vincent Bernat <bernat at luffy dot cx>
 Han Boetes <han at mijncomputer dot nl>
 Robert J. Chassell <bob at rattlesnake dot com>
 Romain Francoise <romain at orebokech dot com>

src/xterm.c

@@ -380,6 +380,11 @@ static void
 x_flush (f)
      struct frame *f;
 {
+  /* Don't call XFlush when it is not safe to redisplay; the X
+     connection may be broken.  */
+  if (!NILP (Vinhibit_redisplay))
+    return;
+
   BLOCK_INPUT;
   if (f == NULL)
     {