[Draft] ASAN heap-use-after-free in fts_get_table_name_prefix

==6466==ERROR: AddressSanitizer: heap-use-after-free on address 0x60300006a210 at pc 0x7efdda35920b bp 0x7efd21814190 sp 0x7efd21813938

READ of size 2 at 0x60300006a210 thread T23

    #0 0x7efdda35920a in __interceptor_strlen (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x7020a)

    #1 0x55e020689b86 in fts_get_table_name_prefix(fts_table_t const*) /home/travis/src/storage/innobase/fts/fts0sql.cc:108

    #2 0x55e020689d96 in fts_get_table_name(fts_table_t const*, char*) /home/travis/src/storage/innobase/fts/fts0sql.cc:146

    #3 0x55e02064bb93 in fts_write_node(trx_t*, que_fork_t**, fts_table_t*, fts_string_t*, fts_node_t*) /home/travis/src/storage/innobase/fts/fts0fts.cc:3878

    #4 0x55e02064cd12 in fts_sync_write_words /home/travis/src/storage/innobase/fts/fts0fts.cc:4047

    #5 0x55e02064d91e in fts_sync_index /home/travis/src/storage/innobase/fts/fts0fts.cc:4128

    #6 0x55e02064efc6 in fts_sync /home/travis/src/storage/innobase/fts/fts0fts.cc:4373

    #7 0x55e02064f712 in fts_sync_table(dict_table_t*, bool, bool, bool) /home/travis/src/storage/innobase/fts/fts0fts.cc:4458

    #8 0x55e02066ff4a in fts_optimize_sync_table(unsigned long) /home/travis/src/storage/innobase/fts/fts0opt.cc:2829

    #9 0x55e0206705e4 in fts_optimize_thread /home/travis/src/storage/innobase/fts/fts0opt.cc:2942

    #10 0x7efdd8d9c6b9 in start_thread (/lib/x86_64-linux-gnu/libpthread.so.0+0x76b9)

    #11 0x7efdd823141c in clone (/lib/x86_64-linux-gnu/libc.so.6+0x10741c)

ASAN:SIGSEGV

perl ./runall-new.pl --basedir=/home/travis/server --vardir=/home/travis/logs/vardir --duration=350 --threads=6 --seed=1547296526 --short-column-names --reporters=Backtrace,ErrorLog,Deadlock --validators=TransformerNoComparator --transformers=ExecuteAsExecuteImmediate,ExecuteAsInsertSelect,ExecuteAsUpdateDelete --redefine=conf/mariadb/alter_table.yy --redefine=conf/mariadb/instant_add.yy --redefine=conf/mariadb/modules/alter_table_columns.yy --redefine=conf/mariadb/sp.yy --redefine=conf/mariadb/bulk_insert.yy --redefine=conf/mariadb/modules/admin.yy --redefine=conf/mariadb/modules/foreign_keys.yy -redefine=conf/mariadb/modules/locks.yy --redefine=conf/mariadb/modules/sql_mode.yy --redefine=conf/mariadb/redefine_temporary_tables.yy --redefine=conf/mariadb/versioning.yy --redefine=conf/mariadb/sequences.yy --filter=/home/travis/mariadb-toolbox/travis/10.4-combo-filter.ff --mysqld=--log_output=FILE --mysqld=--max-statement-time=15 --mysqld=--lock-wait-timeout=10 --mysqld=--loose-innodb-lock-wait-timeout=5 --mysqld=--loose-debug_assert_on_not_freed_memory=0 --mysqld=--innodb-buffer-pool-size=2G --grammar=conf/engines/innodb/full_text_search.yy --gendata=conf/engines/innodb/full_text_search.zz --mysqld=--innodb-page-size=8K