do not check truth value of flex arrays

There is no point in checking "!ref->name" when ref is a
"struct ref". The name field is a flex-array, and there
always has a non-zero address. This is almost certainly not
hurting anything, but it does cause clang-3.6 to complain.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

remote-curl.c

@@ -514,7 +514,7 @@ static int fetch_git(struct discovery *heads,
 	argv[argc++] = url;
 	for (i = 0; i < nr_heads; i++) {
 		struct ref *ref = to_fetch[i];
-		if (!ref->name || !*ref->name)
+		if (!*ref->name)
 			die("cannot fetch by sha1 over smart http");
 		argv[argc++] = ref->name;
 	}