index-pack: don't leak leaf delta result

Another (but minor this time) fallout from commit 9441b61 (index-pack:
rationalize delta resolution code, 2008-10-17).

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

index-pack.c

@@ -550,8 +550,10 @@ static void find_unresolved_deltas(struct base_data *base,
 		find_delta_children(&base_spec, &ofs_first, &ofs_last);
 	}
 
-	if (ref_last == -1 && ofs_last == -1)
+	if (ref_last == -1 && ofs_last == -1) {
+		free(base->data);
 		return;
+	}
 
 	link_base_data(prev_base, base);