Don't set cmd[0] to the window ID

Ahoy,

the attached patch fixes a tiny issue with tabbed. When running it
without a command and having it run spawn(), it tried to execute its
window ID as a command. While most people probably don't have
executables called 341123 or the like in their path, I think that is not
exactly intended. The following patch fixes that:

From c7ade36f8ef6429546ad89bc9ab479fa44c4790a Mon Sep 17 00:00:00 2001
From: Gregor Best <gbe@ring0.de>
Date: Sun, 7 Jul 2013 20:36:06 +0200
Subject: [PATCH] Don't set cmd[0] to the window ID

Starting tabbed without a command sets cmd[0] to the window ID of
tabbed. This leads to funky errors such as "execvp: <ID> failed: no such
file or directory" when running spawn().

Signed-off-by: Gregor Best <gbe@ring0.de>
Signed-off-by: Christoph Lohmann <20h@r-36.net>

tabbed.c

@@ -856,6 +856,8 @@ setcmd(int argc, char *argv[], int replace) {
 	int i;
 
 	cmd = emallocz((argc+2) * sizeof(*cmd));
+	if (argc == 0)
+		return;
 	for(i = 0; i < argc; i++)
 		cmd[i] = argv[i];
 	cmd[(replace > 0)? replace : argc] = winid;