apply: release memory for fn_table

The fn_table is used to record the result of earlier patch application in
case a hand-crafted input file contains multiple patches to the same file.
Both its string key (filename) and the contents are borrowed from "struct
patch" that represents the previous application in the same apply_patch()
call, and they do not leak, but the table itself was not freed properly.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/apply.c

@@ -3724,7 +3724,6 @@ static int apply_patch(int fd, const char *filename, int options)
 	struct patch *list = NULL, **listp = &list;
 	int skipped_patch = 0;
 
-	memset(&fn_table, 0, sizeof(struct string_list));
 	patch_input_file = filename;
 	read_patch_file(&buf, fd);
 	offset = 0;
@@ -3791,6 +3790,7 @@ static int apply_patch(int fd, const char *filename, int options)
 
 	free_patch_list(list);
 	strbuf_release(&buf);
+	string_list_clear(&fn_table, 0);
 	return 0;
 }