BUG#22963169 MYSQL CRASHES ON CREATE FULLTEXT INDEX

The crash is because of length mismatch.

since the max length for FTS token now is larger than 255, so
we will need to signify length byte itself, so only 1 to 128
bytes can be used for 1 bytes, larger than that 2 bytes.

Reviewed-by: Jimmy Yang <jimmy.yang@oracle.com>
RB: 12334

Author: Shaohua Wang

storage/innobase/row/row0ftsort.cc

@@ -512,8 +512,18 @@ row_merge_fts_doc_tokenize(
 		dfield_dup(field, buf->heap);
 
 		/* One variable length column, word with its lenght less than
-		fts_max_token_size, add one extra size and one extra byte */
-		cur_len += 2;
+		fts_max_token_size, add one extra size and one extra byte.
+
+		Since the max length for FTS token now is larger than 255,
+		so we will need to signify length byte itself, so only 1 to 128
+		bytes can be used for 1 bytes, larger than that 2 bytes. */
+		if (t_str.f_len < 128) {
+			/* Extra size is one byte. */
+			cur_len += 2;
+		} else {
+			/* Extra size is two bytes. */
+			cur_len += 3;
+		}
 
 		/* Reserve one byte for the end marker of row_merge_block_t. */
 		if (buf->total_size + data_size[idx] + cur_len