pack-redundant: plug memory leak

Identified via Coverity.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

builtin/pack-redundant.c

@@ -442,6 +442,7 @@ static void minimize(struct pack_list **min)
 	/* return if there are no objects missing from the unique set */
 	if (missing->size == 0) {
 		*min = unique;
+		free(missing);
 		return;
 	}