ioctl(TIOCSWINSZ) will sporadically fail with an ENXIO.  Ignoring this
harmless condition doesn't affect tmux behavior.
In-house patch.  Has been filed upstream as ticket #158
    https://sourceforge.net/p/tmux/tickets/158/
As of filing time, too early to determine whether it will be accepted or not.
--- ORIGINAL/server-client.c	2013-03-26 12:22:31.000000000 -0700
+++ tmux-1.8/server-client.c	2014-09-15 07:56:17.821757634 -0700
@@ -541,7 +541,7 @@
 		 * other platforms and ignoring it doesn't seem to cause any
 		 * issues.
 		 */
-		if (errno != EINVAL)
+		if (errno != EINVAL && errno != ENXIO)
 #endif
 		fatal("ioctl failed");
 	}