rec_get_converted_size_comp_prefix_low: Conditional jump or move depends on uninitialised value upon adding FULLTEXT index

--source include/have_innodb.inc

CREATE TABLE t1 (c CHAR(255)) ENGINE=InnoDB;

INSERT INTO t1 VALUES ('alternative'),('minds');

ALTER TABLE t1 ADD FULLTEXT INDEX (c);

# Cleanup

DROP TABLE t1;

==5989== Thread 29:

==5989== Conditional jump or move depends on uninitialised value(s)

==5989==    at 0x106EF79: unsigned long rec_get_converted_size_comp_prefix_low<false>(dict_index_t const*, dfield_t const*, unsigned long, unsigned long*, rec_comp_status_t, bool) (rem0rec.cc:1191)

==5989==    by 0x106A179: rec_get_converted_size_temp(dict_index_t const*, dfield_t const*, unsigned long, unsigned long*, rec_comp_status_t) (rem0rec.cc:1796)

==5989==    by 0x109F2FC: row_merge_buf_encode(unsigned char**, dict_index_t const*, mtuple_t const*, unsigned long) (row0merge.cc:317)

==5989==    by 0x10A1397: row_merge_buf_write(row_merge_buf_t const*, merge_file_t const*, unsigned char*) (row0merge.cc:1021)

==5989==    by 0x1076905: fts_parallel_tokenization(void*) (row0ftsort.cc:963)

==5989==    by 0x4E3F493: start_thread (pthread_create.c:333)

==5989==    by 0x6A9A93E: clone (clone.S:97)

==5989== Conditional jump or move depends on uninitialised value(s)

==5989==    at 0x106F3AF: unsigned long rec_get_converted_size_comp_prefix_low<false>(dict_index_t const*, dfield_t const*, unsigned long, unsigned long*, rec_comp_status_t, bool) (rem0rec.cc:1235)

==5989==    by 0x106A179: rec_get_converted_size_temp(dict_index_t const*, dfield_t const*, unsigned long, unsigned long*, rec_comp_status_t) (rem0rec.cc:1796)

==5989==    by 0x109F2FC: row_merge_buf_encode(unsigned char**, dict_index_t const*, mtuple_t const*, unsigned long) (row0merge.cc:317)

==5989==    by 0x10A1397: row_merge_buf_write(row_merge_buf_t const*, merge_file_t const*, unsigned char*) (row0merge.cc:1021)

==5989==    by 0x1076905: fts_parallel_tokenization(void*) (row0ftsort.cc:963)

==5989==    by 0x4E3F493: start_thread (pthread_create.c:333)

==5989==    by 0x6A9A93E: clone (clone.S:97)