refs: release strbuf on error return in write_pseudoref()

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -612,7 +612,7 @@ static int write_pseudoref(const char *pseudoref, const unsigned char *sha1,
 	if (fd < 0) {
 		strbuf_addf(err, "could not open '%s' for writing: %s",
 			    filename, strerror(errno));
-		return -1;
+		goto done;
 	}
 
 	if (old_sha1) {