xD/xS: NICK without USER would block nicks forever

xD.c

@@ -887,7 +887,14 @@ static void
 client_unregister (struct client *c, const char *reason)
 {
 	if (!c->registered)
+	{
+		if (c->nickname)
+		{
+			str_map_set (&c->ctx->users, c->nickname, NULL);
+			cstr_set (&c->nickname, NULL);
+		}
 		return;
+	}
 
 	char *message = xstrdup_printf (":%s!%s@%s QUIT :%s",
 		c->nickname, c->username, c->hostname, reason);

xS/xS.go

@@ -910,6 +910,10 @@ func (c *client) nicknameOrStar() string {
 
 func (c *client) unregister(reason string) {
 	if !c.registered {
+		if c.nickname != "" {
+			delete(users, ircToCanon(c.nickname))
+			c.nickname = ""
+		}
 		return
 	}