index_mem(): check return value of fsck_finish()

This would catch problems in blobs that were newly linked to git
metafiles (like .gitmodules) by a tree we are checking. We should add a
test.

Note that fsck_finish() both checks the blobs and frees the memory. So
in a short-circuit "||", we'd fail to do that cleanup if fsck_buffer()
reports a problem. That's OK in this case because we die(). Maybe this
should stay as two separate conditionals.

Author: peff

object-file.c

@@ -1298,9 +1298,9 @@ static int index_mem(struct index_state *istate,
 		fsck_options_init(&opts, the_repository, FSCK_OPTIONS_DEFAULT);
 		opts.strict = 1;
 		opts.error_func = hash_format_check_report;
-		if (fsck_buffer(null_oid(istate->repo->hash_algo), type, buf, size, &opts))
+		if (fsck_buffer(null_oid(istate->repo->hash_algo), type, buf, size, &opts) ||
+		    fsck_finish(&opts))
 			die(_("refusing to create malformed object"));
-		fsck_finish(&opts);
 	}
 
 	if (write_object)